高中英语情态动词讲解与练习(含答案)
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高中英语语法之情态动词
（一）情态动词的定义 ：情态动词表示说话人对某一动作或状态的态度。
（二）情态动词的特点 ：1）有一定词义；2）不受主语人称和数的变化影响；3）与主要动词的原形（或称不带to的不定式）一起构成谓语（除ought to作固定词组看待）。
情态动词无人称和数的变化, 情态动词后面跟的动词需用原形,否定式构成是在情态动词后面加 "not"。 个别情态动词有现在式和过去式两种形式, 过去式用来表达更加客气, 委婉的语气, 时态性不强, 可用于过去，现在或将来。情态动词属非及物动词，故没有被动语态。
He could be here soon. 他很快就来。 We can't carry the heavy box. 我们搬不动那箱子。
I'm sorry I can't help you. 对不起，我帮不上你。
基本助动词与情态助动词最主要的区别之一是，基本助动词本身没有词义，而情态助动词则有自己的词义，能表示说话人对有关动作或状态的看法，或表示主观设想：
What have you been doing since （构成完成进行体，本身无词义）
I am afraid I must be going. （一定要）
You may have read some account of the matter. （或许已经）
除此之外，情态助动词还有如下词法和句法特征：
1） 除ought和used以外，其他情态动词后面只能接不带to的不定式。如果我们把ought to和used to看做是固定词组的话，那么，所有情态动词无一例外地只能接不带to的不定式：
We used to grow beautiful roses.
I asked if he would come and repair my television set.
2） 情态助动词在限定动词词组总是位居第一： They need not have been punished so severely.
3） 情态助动词用于第三人称单数现在时的时候，没有词形变化，即其词尾无-s形式：
She dare not say what she thinks.
4） 情态动词没有非限定形式，即没有不定式和分词形式，也没有相应的动名词：
Still, she needn't have run away.
5） 情态助动词的“时”的形式并不是时间区别的主要标志。在不少场合，情态助动词的现在时和过去时形式都可以表示现在、过去或将来时间： Would you mind very much if I ask you to do something She told him he ought not to have done it.
6） 情态助动词之间是相互排斥的，即在一个限定动词词组中只能出现一个情态助动词，但有时却可以与have和be基本助动词连用： You should have washed the wound.
Well, you shouldn't be reading a novel.
（三）情态动词有四类：①只做情态动词：must,can(could),may(might),ought to ②可做情态动词又可做实义动词：need,dare ③可做情态动词又可做助动词：shall(should),will(would)
④具有情态动词特征：have(had,has) to,used to ⑤情态动词表猜测
（四）情态动词的基本用法
1. can (could)
1）表示能力，could主要指过去时间。
Two eyes can see more than one. 两只眼比一只眼看得清。
Could the girl read before she went to school 这女孩上学前能识字吗？
2）表示可能（理论上或是逻辑判断上）。
The temperature can fall to –60℃, that is 60℃ below freezing.
气温可降至—60℃，也就是零下60℃。
He can t (couldn t) have enough money for a new car. 他不可能有足够的钱买新车。
You mustn t smoke while you re walking around in the wood. You could start a fire.
在林子里走时勿吸烟，那样可能会引起火灾。
3）表示允许。
Can I have a look at your new pen 我可以看一看你的新钢笔吗？
He asked whether he could take the book out of the reading—room.
他问他可不可以把书带出阅览室。
4）表惊异、怀疑、不相信等态度。主要用于否定句、疑问句或感叹句中。
Where can (could) they have gone to 他们会去哪儿了呢？
He can t (couldn t) be over sixty. 他不可能超过六十岁。
How can you be so careless 你怎么这么粗心？
5）比较委婉客气地提出问题或陈述看法。
Can (Could) you lend me a hand 帮我一把好吗？
I m afraid we couldn t give you an answer today. 恐怕我们今天不能给你答复。
2. may (might)
1）表允许，might可以指过去时间，也可指现在时间，语气更委婉。
You may take whatever you like. 你喜欢什么就拿什么。
He told me that I might smoke in the room. 他告诉我可以在房间里抽烟。
May (Might) I ask for a photo of your baby 我可以要一张你宝宝的照片吗？
在回答以may引起的问句时，多避免用这个词，而用其它方式，如Yes, please. / Certainly.
/ Please don t ./ You d better not. / No, you mustn t.等，以免显得太严峻或不客气。
2）表可能（事实上）。可以指过去时间，也可以指现在时间，但语气更加不肯定。
He may be at home. 他可能在家。
She may not know about it. 她可能不知道这件事。
He was afraid they might not agree with him. 他担心他们可能不同意他的意见。
They might be having a meeting, but I m not sure. 他们有可能在开会，不过我不肯定。
3. must
1）表示义务。意为“必须”（主观意志）。
We must do everything step by step. 我们一切都必须循序渐进地做。
You mustn t talk to her like that. 你不可能那样对她说话。
--Must we hand in our exercise—books now 我们现在就要交练习本吗？
--No, you needn t. / No, you don t have to. 不必。（这种情况下，一般不用mustn t）
2）表示揣测。意为“想必、准是、一定”等，只用于肯定句。
He must be ill. He looks so pale. 他准是病了。他的脸色苍白。
She s wearing a diamond necklace. She must have a lot of money.
她戴着钻石项链，一定很有钱。
4. shall
1）表征询意见，用于第一、第三人称疑问句。
Shall I get you some tea 我给你点茶好吗？
Shall the boy wait outside 让那男孩在外面等吗？
What shall we do this evening 我们今晚做什么？
2）表说话人的意愿，有“命令、允诺、警告、决心”等意思，用于第二、第三人称陈述句。
You shall do as I say. 按我说的做。（命令）
You shall have my answer tomorrow. 你明天可以得到我的答复。（允诺）
He shall be sorry for it one day, I tell you. 有一天他会后悔的，我告诉你。（警告）
Nothing shall stop us from carrying out the plan. 什么也不能阻止我们执行这项计划（决心）
5. will
1）表意愿，用于各种人称陈述句。
I will do anything for you. 我愿为你做任何事。
None is so blind as those who won t see. 不愿看的人眼最瞎。
If you will read the book, I ll lend it to you. 如果你愿意读这本书，我会把它借给你。
2）表请求，用于疑问句。
Will you close the window It s a bit cold. 请你把窗户关上好吗？有点冷。
Won t you drink some more coffee 再来一点咖啡好吗？
3）表示某种倾向或习惯性动作。
Fish will die out of water. 鱼离开水就不能活。 The door won t open. 这门打不开。
The boy will sit there hour after hour looking at the traffic go by.
那男孩常常坐在那里好几个钟点，看着车辆行人通过。
6. should
1）表义务。意为“应该”（某件事宜于做），用于各种人称。
You should be polite to your teachers. 你对老师应该有礼貌。
You shouldn t waste any time. 你不应该浪费时间。
2）表推测，意为“想必一定、照说应该、估计”等。
The film should be very good as it is starring first—class actors.
这部新电影是一流演员主演的，估计拍得很好。
They should be home by now. 照说他们现在应当已经到家了。
7.would
1）表意愿。
They would not let him in because he was poorly dressed. 他们不让他进去因为他衣着旧。
I said I would do anything for you. 我说过我愿意为你做任何事。
2）表委婉地提出请求、建议或看法。
Would you like another glass of beer 再来杯啤酒好吗？
Would you mind cleaning the window 请把窗户擦一下好吗？
They wouldn t have anything against it. 他们不会有什么反对意见。
3）表过去反复发生的动作或过去的一种倾向。
Every time she was in trouble, she would go to him for help.
她每遇到麻烦都会向她求助。他告诉我盒子打不开了。
8. ought to
1）表义务，意为“应该”（因责任、义务等该做），口气比should稍重。
You are his father. You ought to take care of him. 你是他父亲，应当管他。
You oughtn t to smoke so much. 你不应该抽这么多烟。
2）表推测，暗含很大的可能，语气较弱。
Han Mei ought to know his telephone number. 韩梅该知道他的电话号码。
There s a fine sunset; it ought to be a fine day tomorrow. 今天有晚霞，明天应该是个好天。
9. used to
表示过去的习惯动作或状态，现在不复发生或存在。疑问式和否定式有两种。
He used to live in the countryside, but now he lives in the city.他过去住在乡下，现在住在城里。
There used to be a building at the street corner, but it has been pulled down.
街道拐角处过去有座楼房，现在拆了。
I usedn t (didn t use) to smoke. 我过去不抽烟。
Used you (Did you use) to go to school on foot 你过去常步行去学校吗？
（五）其他用法
首先它是动词，而且不同于行为动词，行为动词表示的是可以通过行为来表达的动作（如写，读，跑），而情态动词只是表达的一种想法（如能，也许，敢）。
用法是：情态动词+行为动词原形
例句：I can read this sentence in English. 我能用英语读这句话。
情态动词是一种本身有一定的词义,表示说话人的情绪,态度或语气的动词,但不能单独作谓语, 只能和其他动词原形构成谓语。
We can be there on time tomorrow.我们明天能按时去那儿。
May I have your name 我能知道你的名字吗？
Shall we begin now 我们现在就开始吗？
You must obey the school rules.你必须遵守校规。
情态动词数量不多,但用途广泛,主要有下列: can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would),have (to) ,had better.
情态动词还有一个很重要的用法，即情态动词表推测——
情态动词表推测的用法小结
（一）情态动词表推测的三种句式
1.在肯定句中一般用must (一定)，may（可能），might / could（也许，或许）。
（1）He must/may/might know the answer to this question
他一定/可能/也许知道这个问题的答案。
（2）It is cold in the room. They must have turned off the heating.
屋里很冷，他们肯定把暖气关了。
2.否定句中用can’t / couldn’t(不可能), may not/might not(可能不)。
（1）It can’t/couldn’t be the headmaster. He has gone to America.
这不可能是校长，他去美国了。
（2）He may not/might not know the scientist. 他也许不认识那位科学家。
3.疑问句中用can/could (能…… )。
（1）Could he have finished the task 他可能把任务完成了吗？
（2）Can he be at home now 他现在能在家吗？
注：以上三种句式中情态动词的语气按程度都是依次递减的。Might, could并非may, can的过去式，而表示语气较为委婉或可能性较小。
（二）情态动词表推测的三种时态
1.对将来情况的推测，用“情态动词 + 动词原形”。
（1）She must / may / might / could arrive before 5. 5:00前她一定/可能/也许到。
（2）She must/may/might/could walk miles and miles among the hills without meeting anyone.
她一定/可能/也许会在山里一连走好几英里而遇不到一个人。
2.对现在或一般情况的推测，用“情态动词 + be”，“情态动词 +be doing”或“情态动词 + 动词原形”。
（1）He must / may / might / could be listening to the radio now.
他一定/可能/也许正在听收音机。
（2）He can’t ( couldn’t ) / may ( might ) not be at home at this time.
这个时候他不可能/可能不在家。
（3）Mr. Bush is on time for everything .How can ( could ) he be late for the opening ceremony
布什先生一向准时，这次开幕式他怎么可能迟到呢？
3.对过去情况的推测，用“情态动词 + have +过去分词”。
（1）It must / may / might / could have rained last night .The ground is wet.
地湿了，昨晚肯定/可能/也许下雨了。
（2）The door was locked. He can ( could ) not / may ( might ) not have been at home .
门锁着，他不可能/可能不在家。
（3）Can / Could he have gotten the book？
难道他找到书了吗？
注：情态动词 should /ought to表推测时，意为“想必会，理应……”但与“have +过去分词”连用时，则又可构成虚拟语气意为“本应该做某事却没做”。例如：
（4）It’s seven o’clock. Jack should/ought to be here at any moment.
现在七点钟了，杰克理应随时到达。（推测）
（5）She should / ought to have attended your birthday party, but she had to look after her mother in hospital. （虚拟） 她本该出席你的生日晚会的，可是她得在医院照顾她妈妈。
（6）Tom should not /ought not to have told me your secret, but he meant no harm. （虚拟） 汤姆本不该告诉我你的秘密，可是他并无恶意。
（六）功能
助动词(auxiliary)主要有两类：基本助动词(primary auxiliary)和情态助动词(modal auxiliary)。基本助动词有三个：do, have和be；情态助动词基本的有十四个：may, might; can, could; will, would; shall, should; must, need, dare, used to, ought to.had better 上述两类助动词的共同特征是，在协助主动词构成限定动词词组时，具有作用词的功能：
1） 构成否定式：
He didn't go and neither did she. The meeting might not start until 5 o'clock.
2） 构成疑问式或附加疑问式：
Must you leave right now You have been learning French for 5 years, haven't you
3） 构成修辞倒装：
Nowhere can he obtain any information about his sister.
Hardly had he arrived when she started complaining.
4） 代替限定动词词组：
A: Who can solve this crossword puzzle B: Tom can.
A: Shall I write to him B: Yes, do.
重点疑难
（一）need和dare的用法
need和dare既可用作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句和疑问句。用作实义动词时，可用于各种句式。
1.用作情态动词
--Need I come --Yes, you must. --我需要来吗？ --需要。
You needn t telephone him now. 你现在不必打电话给他。
I don t think you need worry. 我想你不必发愁。
She dare not go out alone at night. 她晚上不敢一个人出去。
How dare you say I m unfair 你竟敢说我不公平？
Not one of them dared mention this. 他们谁也不敢提这件事。
2.用作实义动词
You don t need to do it yourself. 你不必亲自做这件事。
We need to tell them the news. 我们需要把这消息告诉他们。
The table needs painting (to be painted.). 桌子需要油漆一下。
We should dare to give our own opinion. 我们要敢于提出自己的观点。
He did not dare (to) look up. 他不敢抬头看。
I dare day he ll come again. 我想他会再来的。 （cI dare say…为固定习语）
（二）情态动词后跟完成式和进行式的用法
1.情态动词后跟完成式，表“应当已经……”，“想必已经……”，“本来可以……”等意。
I should have finished the work earlier. 我应当早一点完成这项工作的。
He isn t here. He must have missed the train. 他还未到，一定是没赶上火车。
Where can (could) he have gone 他能到那里去了呢？
You may (might) have read about it. 你可能在报上已经读到这件事了。
You could (might) have been more careful. 你本来可以更细心的。
He needn t have worried about it. 他本不必为此事担心。
There was a lot of fun at yesterday s party. You ought to have come, but why didn t you
昨天的聚会非常有意思。你本应该来，为何不来呢？
2. 情态动词后跟进行式，表示“想必正在……”，“可能正在……”，“应当正在”等意。
It s twelve o clock. They must be having lunch. 现在是十二点。他们一定正在吃饭。
They may be discussing this problem. 他们可能正在论讨这个问题。
He can t be telling the truth. 他说的不可能是真话。
She shouldn t be working like that. She s still so weak. 她不应当那样干，她身体仍那么虚。
（三）几组词的辨异
1. can 和be able to
1）情态动词can只有两种时态形式，现在式can和过去式could，而be able to有多种时态形式。
Mary can play the piano. She has been able to play it since she was 5.
玛丽会弹钢琴。她五岁起就会弹了。
2）用在过去时中，could经常表示能够做某事，事实上不一定去做，而was∕were able to则表示“过去做成了某事”。在否定句中两者可通用。
He could swim across the English Channel. But he didn t feel like it that day.
他能游过英吉利海峡，但那天他不想游。
Yesterday I was able to get home before the heavy rain. 昨天我在下大雨前赶到了家里。
2. must和 have to
must表示主观意志，而have to表示由于客观因素不得不做某事。must没有过去式，除在间接引语中可用于表示过去时间，在直接引语中表示过去时间应该用had to代替。
I told her that she must give up smoking. 我叫她必须戒烟。
We had to get everything ready that night. 我们那晚得把一切准备就绪。
3. would和used to
1）used to表示过去与现在或过去某时与后来的情况有不同，而would只表过去的情况。People used to think that the earth was flat.
过去人们认为地球是平的。（现在人们不这么认为。）
She would go out for a walk in the morning when she was in the country.
在乡下时，她总是在早晨去散会儿步。（可能现在仍有散步的习惯。）
2）used to可表示过去的习惯动作和经常的情况，而would只表示过去的习惯动作。
He used to ∕would smoke while writing. 过去他写东西时常抽烟。
She used to be fat. 她过去很胖
专项练习（一）
1. I __________ you, because I thought I must be wrong.
A. dare not ask B. dare not to ask C. dare not asking D. dare to not ask
2. There __________ some flowers in the garden.
A. were used to be B. used to be C. uses to be D. used to be having
3. “__________ I take it out ” “I m sorry, you __________.”
A. Could …couldn t B. Might…might not C. Could…can D. May…can t
4. You were stupid to climb the tree. You __________ hurt yourself.
A. may B. might C. will D. might have
5. You __________ those letters. Why didn t you
A. should post B. should have posted C. must have posted D. ought to post.
6. All the lights are on, the Smiths __________ up.
A. must get B. is getting C. must be getting D. would get
7. He __________ lead a horse to the water but he __________ not make it drink.
A. will…can B. may…can C. may…dares D. dare…can
8. “Need we do this job now ” “Yes, __________.”
A. you need B. you should C. you must D. you can
9. __________ to have lunch with us today
A. Do you likes B. Would you like C. Will you liked D. Have you liked
10. He said that you __________ watch TV all the evening if you wished.
A. may B. must C. can D. might
11. –Is John coming by train --He should, but he __________ not. He likes driving his car.
A. must B. can C. need D. may
12. Peter __________ come with us tonight, but he isn t very sure yet.
A. must B. can C. may D. will
13. Michael __________ be a policeman, for he s much too short.
A. needn t B. can t C. shouldn t D. won t
14. I thought you __________ be hungry, so I have brought you some cakes.
A. may B. might C. can D. could
15. I wonder how he __________ that to the teacher.
A. dare to say B. dare saying C. not dare say D. dared say
e on! We __________ hurry because there isn t much time left.
A. may B. must C. can D. need
17. Amy did best in the English test. She __________ hard last week.
A. must have working B. should have worked C. should work D. must work
18. The fire spread through the hotel very quickly but everyone __________ get out.
A. had to B. would C. could D. was able to
19. –--I stayed at a hotel while in New York. ---Oh, did you You __________ with Barbara.
A. could have stayed B. could stay C. would stay D. must have stayed
20. It s nearly seven o clock. Jack __________ be here at any moment.
A. must B. need C. should D. can
答案： 1.A2.B3.D4.D5.B6.C7.B8.C9.B10.D11.D12.C13.B14.B15.D16.B17.A18.D19.A20.
专项练习（二）
1. Jean have kept his promise. I wonder why he changed his idea.
A. must B. should C. need D. would
2. Jane have come to the party, but she not find the exact time.
A. could; could B. might; could C. should; could D. should; would
3. So many mistakes in your homework! You more careful.
A. may be B. had to C. would be D. should have been
4．Her brother be at home now, because he was seen playing basketball in the stadium just now. A. mustn’t B. needn’t C. can’t D. shouldn't
5．---I can’t understand why our boss is late. ---He the early bus.
A. could miss B. may have missed C. can have missed D. might miss
6. She didn't answer the phone, she ______ asleep.
A. may be B. must be C. should have been D. must have been
7．The little girl’s eyes were red. She ______.
A. may cry B. must cry C. must be cried D. must have been crying
8．He______ his supper now, for the dining hall is still closed.
A. can’t be having B. needn’t be having C. mustn’t be having D. shouldn't be having
9．I parked my bike behind the building, but now it is gone. It ________ .
A. may be stolen B. must be stolen C. must have been stolen D. must have stolen
10. ______ Mr. Black_______go to work by ferry before the bridge was built
A. Did; used to B. Use; to C. Did; use to D. Does; use to
11. The hotel is only a stone’s throw away, you ______ take a bus.
A. need not to B. not need to C. don't need D. need not
12. I am busy now, _______ my brother do it for you
A. Will B. Shall C. Must D. May
13. ---You needn’t do it right now, need you ---Yes I am afraid I ______ .
A. need B. needn’t C. must D. mustn’t
14.My English-Chinese dictionary has disappeared . Who _____ have taken it (2003年上海春季高考) A. should B. must C. could D. would
15. ---The room is so dirty._______ we clean it ----Of course. (2003年北京春季高考)
A． Will B. Shall C. Would D. Do
16. If you have something important to do, you ______ waste any time.
A. needn’t B. mustn’t C. may not D. won’t
17. If you want to borrow a football after school, your student card______ here.
A. has to leave B. must leave C. has to be left D. must be left
18. “ Did you scold him for his carelessness ” “Yes, but _____ it”
A. I’d rather not do B. I’d rather not have done C. I shouldn’t do D. I’d better not do
19. “ Don’t get near to it . It is too dangerous!” “_______” .
A. Yes, I won’t B. No, I don’t C. No, I can’t D. No, I won’t
20. He must be in the classroom, _______ he
A. mustn’t B. can’t C. isn’t D.can
21. He________ be in the garden. He must be in the room.
A. can’t B. mustn’t C. will not D. may not
22. “Do you have to leave now ” “I am very sorry, but I really______.”
A. can’t B. have C. should D. must
23. “Let’s go to the library, shall we ” “_________ ”
A. No, I can’t B. Yes, I will C. Yes , thank you D. No, we’d better not
24. “Can I take it away ” “ You ______ better not.”
A. should B. could C. would D. had
25. You _______ have brought your camera. They all had theirs with them.
A. couldn’t B. needn’t C. wouldn’t D. mustn’t
26. See who is there!______it be May
A. May B. Must C. Can D. Will
27. John______ be a basketball player. He is much too short.
A. may B. mustn’t C. can’t D. should
28. The Chinese teacher looks so pale. She ______ be ill.
A. must B. mustn’t C. can D. need
29. Something______to save our earth. Do you think so
A. can do B. must do C. has to do D. must be done
30. Look at what you have done! You ______ be more careful.
A. ought B. can C. would D. should
专项练习（三）
1. — Has Li Lin started He said he would join in the party.
— He ______. He is a man of keeping his word.
A. could have left B. must have left C. can’t come D. won’t be coming
2. — May I park my car here — No, you ______. No car is allowed to park here.
A. may not B. needn’t C. mustn’t D. daren’t
3. — Excuse me, could you tell me where the Yajia Supermarket is
— It’s two blocks straight ahead. You ______ miss it.
A. mustn’t B. can’t C. needn’t D. shouldn’t
4. — I saw Mr. Sun at Tongyu Station this morning.
— You ______. He’s still on holiday in Hawaii.
A. couldn’t have B. mustn’t have C. shouldn’t D. needn’t
5. — How about paying a visit to Dr. Wang, our former Chinese teacher
— Good idea. I will e-mail him today so that he ______ know ______ to expect us.
A. shall; why B. could; when C. would; what D. will; how
6. Everything has two sides. Beautiful songs, sometimes, ______ be just noise to others.
A. must B. may C. should D. could
7. Someone ______ my umbrella. I found it wet yesterday.
A. must be using B. must have used C. must use D. must have been using
8. — How dangerous it was!— Yes, but for the passer-by’s quick action, the girl ______.
A. was drowned B. could have been drowned C. had drowned D. should be drowned
9. You ____ scold such a pupil who always keeps silent so seriously that you _____ hurt him.
A. should; can B. may; will C. mustn’t; may D. can’t; must
10. — Why does Alice know so much about Angkor Wat — She ______ have been there, or ...
A. must B. oughtn’t to C. may D. can’t
11. — You may laugh, but I’ve been thinking of becoming a vegetarian.— Oh, you ______ be crazy. You will be hungry all the time.
A. must B. may C. will D. need
12. — What’s the matter with you
— Oh, I’m not feeling well in the stomach. I ______ so much fried fish just now.
A. shouldn’t eat B. mustn’t have eaten C. shouldn’t have eaten D. mustn’t eat
13. — ______ he have been chosen as captain of the football team — Yes, he ______.
A. Can; must have B. Must; must have C. Can; must D. Must; must
14. Mr. Zhang ______ in Shanghai tomorrow morning.
A. can have arrived B. will have arrived C. may have arrived D. must have arrived
15. Miss Wang started at 8 o’clock, and she ______ be there now.
A. should B. can C. can’t D. need
16. — It must be Mr. Li who did it. — No, it ______ be Mr. Li.
A. mustn’t B. wouldn’t C. can’t D. may
17. You ______ finish reading the book as soon as possible.
A. may B. can C. need D. should
18. — Need you go to work now — Yes, I ______.
A. must B. need C. can D. dare
19. Your trousers are dirty. ______ them for you
A. Shall I wash B. Will I wash C. Am I going to wash D. Am I washing
20. You are late for school today. You ______ to school earlier.
A. ought to come B. should have come C. ought have come D. should come
21. We must learn from Lei Feng, ______ we
A. may B. can’t C. don’t D. needn’t
22. She must be hungry, ______ she
A. isn’t B. needn’t C. doesn’t D won’t
23. He ought to come here early, ______ he
A. would B. should C. didn’t D. shouldn’t
24. You used to smoke, ______ you
A. used to B. don’t C. didn’t D. shouldn’t
25. You ought ______ for what you haven’t done.
A. not to be punished B. not be punished C. to not punished D. to not be punished
26. ______ you please tell me the way to the post office
A. Must B. Need C. Would D. Should
27. I’m sure he ______ have the computer sooner or later.
A. shall B. can C. must D. would
28. It is important that we ______ learn how to drive.
A. have to B. should C. need D. shall
专项练习（四）
1. I didn’t see her in the meeting room this morning. She _____ at the meeting.
A. mustn’t have spoken B. shouldn’t have spoken
C. needn’t have spoken D. couldn’t have spoken
2. One ought _____ for what one hasn’t done.
A. not to be punished B. to not be punished
C. to not punished D. not be punished
3. If you really want yourself to be in good health, you must ___ always ___ so much.
A. not; be smoking B. not; have smoked
C. not; to smoke D. be not; smoking
4. With so much work on hand, you _____ to see the game last night.
A. mustn’t go B. shouldn’t go
C. couldn’t have gone D. shouldn’t have gone
5. Most of the students felt rather disappointed at the English party. They say that it ______ better organized.
A. had been B. had to be C. must have been D. could have been
6. I’m surprised that he _____ in the exam.
A. should fail B. would have failed
C. may have failed D. should have failed
7. The little girl _____ there alone.
A. not dare go B. dares not go C. dare not go D. dare not to go
8. “Must we do it now ” “No, you _____.”
A. won’t B. needn’t C. can’t D. don’t
9. He said he would rather not _____ it right now.
A. doing B. to do C. do D. to be doing
10. You _____ to the meeting this afternoon if you have something important to do.
A. needn’t to come B. don’t need come
C. don’t need coming D. needn’t come
11. Put on more clothes. You _____ be feeling cold with only a shirt on.
A. can B. could C. would D. must
12. I _____ play football than baseball.
A. would rather B. had better C. like better D. prefer
13. I thought you _____ like something to read, so I have brought you some books.
A. may B. might C. could D. must
14. There was plenty of times. She _____.
A. mustn’t have hurried B. couldn’t have hurried
C. must not hurry D. needn’t have hurried
15. The plant is dead. I _____ it more water.
A. will give B. would have given
C. must give D. should have given
16. You _____ return the book now. You can keep it till next week if you like.
A. can’t B. mustn’t C. needn’t D. may not
17. It’s still early, you _____.
A. mustn’t hurry B. wouldn’t hurry
C. may not hurry D. don’t have to hurry
18. Please open the window, _____
A. can’t you B. aren’t you C. do you D. will you
19. We _____ for her because she never came.
A. mustn’t have waited B. shouldn’t have waited
C. mustn’t wait D. needn’t wait
20. — May I stop here — No, you _____.
A. mustn’t B. might not C. needn’t D. won’t
21. It’s a fine day. Let’s go fishing, _____.
A. won’t we B. will we C. don’t we D. shall we
22. I didn’t see her in the meeting room this morning. She _____ at the meeting.
A. mustn’t have spoken B. shouldn’t have spoken
C. needn’t have spoken D. couldn’t have spoken
23. — Please don’t make a noise. — _____. I’ll be as quiet as a mouse.
A. Yes, I won’t B. No, I won’t C. No, I will D. Yes, I will
24. The young man has made so much noise that he _____ not have been allowed to attend the concert.
A. could B. must C. would D. should
25. — Where is John — He _____ in the library.
A. should be B. must be C. can be D. must have been
26. Since the road is wet this morning, _____ last night.
A. it must rain B. it must be raining
C. it must have rained D. it must have been rain
27. — Will your brother stay home tonight
— I’m not quite sure. He _____ to the cinema tonight.
A. must go B. can go C. may go D. may be going
28. She’s already two hours late. What ______ to her
A. can have happened B. may have happened
C. should have happened D. must happen
29. You must be a writer, _____
A. mustn’t you B. are you C. must you D. aren’t you
30. I got up early that morning, but I _____ so because I had no work to do.
A. mustn’t have done B. didn’t need to do
C. needn’t have done D. can’t have done
31. He _____ have come here yesterday, but he didn’t.
A. could B. should C. ought to D. all the above
32. I missed the last bus, so I _____ go home on foot.
A. must B. have to C. may D. had to
33. He ought to win the first prize, _____ he
A. oughtn’t B. shouldn’t C. mustn’t D. both A and B
34. Everyone _____ do his best for the modernizations of our country.
A. can B. may C. should D. might
35. Let’s clean our classroom, _____
A. will you B. don’t we C. shall we D. do you
36. Let us play basketball, ______
A. will you B. don’t we C. shall we D. do you
37. He asked me for this book many times. Please tell him that he _____ have it tomorrow.
A. must B. may C. shall D. both B and C
38. “Your phone number again I _____ quite catch it.” “It’s 9568442.”
A. didn’t B. couldn’t C. don’t D. can’t
39. Mother _____ us stories when we were children.
A. was used to tell B. is used to telling C. used to tell D. used to telling
40. She would rather _____ more money on books _____ on clothes.
A. cost … not B. to spare … don’t C. pay … than D. spend … than
专项练习（二）
1.解析：选B. “should have +过去分词” 表示“过去本来应该(但没能)做某事”；keep one’s promise 意为“信守诺言”。
2.解析：选A.“ could have+过去分词表示过去本来应该(但没能)做某事”。
3.解析：选D. “You should have been more careful”. 意为：你本来应该更细心的。
4．解析：选C. can’t be at home 意为：不可能在家。
5解析：选B. “may have+过去分词”表示对过去动作的判断，意为：可能做了某事。 注意：can表示可能时，只能用于疑问句和反问句。
6.解析：选D. 表示：对过去发生的事情的肯定推测。
7．解析：选D. 意为：她刚才肯定一直在哭。对过去某事正发生的推测。
8．解析：选A. 对现在正在发生的事情的否定推测。
9．解析：选C. 对过去发生的事情 的肯定推测的被动式。
10.解析：选C. used to do的疑问式，可以是Used+主语+to do 或Did +主语+use to do
11.解析：选D. 说话人认为不必要乘车, need 为情态动词。
12.解析：选B. 在疑问句中shall 用于第三人称，也表示征求意见。
13.解析：选C. Yes的意思是：不。意为：恐怕我必须现在就做。
14.解析：选C. could/can have done 用于否定推测和疑问推测。
15.解析：选B. shall 用在疑问句中，常用于第一，三人称， 表示征求意见或请求指示。
16.解析：选B. 根据句意用mustn’t
17.解析：选C. have to 表示客观需要，must表示主观需要。学生证必须放在此是客观需要。
18.解析：选B. would rather 加完成时表示对完成了的或过去了的事情的态度。意为：当时是不情愿做的。
19.解析：选D. A为错误的表达方式；B和C没有直接回答对方的问候。
20.解析：选C. 对表否定的must进行反意疑问时，要用句子的实义动词
21.解析：选A. 否定推测用can’t不用mustn’t
22.解析：选D. 回答have to 的疑问句用must作肯定回答。
23.解析：选D. A,B,C都 不能回答shall we, 此处D的语气比较婉转客气。
24.解析：选D. had better 与不带to 的不定式构成谓语，可以变成疑问句：Hadn’t you better----
25. 解析：选B. 本来不必要做某事.
26. l解析：选C. 表推测时A，B都用作疑问句。
27.解析：选C. 断然的不定推测用can’t
28.解析：选A. 表示有把握的肯定推测用must
29.解析：选D. “something must be done” 意为：必须采取措施。
30. 解析：选D. ought 后应用to
（三）答案及解析：
1. B。从He is a man of keeping his word中可以看出，李林肯定已经出发来参加聚会了，这是对已经发生的事情非常肯定的推测，故用must have done。注意must表推测时，不能用于否定句和疑问句中。
2. C。此题考查以情态动词提问的一般疑问句的回答。在英语中，以某些情态动词提问的句子，出于礼貌委婉或句意的需 要，回答时，要换用另一个情态动词。在回答must开头的一般疑问句时，肯定回答用must，否定回答用needn’t或don’t have to；在回答may开头的一般疑问句时，肯定回答用may，否定回答用mustn’t；在回答need开头的一般疑问句时，肯定回答用must，否定回答用needn’t。
3. B。根据题意，此处需要表示“推测”的否定结构，故can’t为正确答案。4. A。这是一个省略句，couldn’t have done表示对过去发生的动作的否定推测，意为“不可能……”。
5. B。这是一个综合题。本题so that后的目的状语从句中的谓语动词要用“情态动词（ may / might / can / could ） + 动词原形”。When to expect us表示“我们什么时候可到达”。“疑问词+不定式”结构在句中作know的宾语。
6. B。由sometimes可知，此处应用表示可能性不大的情态动词，即may。
7. B。由后句可知，这是对过去发生的事情的肯定推测，故B项正确。
8. B。but for的意思是“要不是”，语法功能上等同于if 引导的否定虚拟条件句，因前句中How dangerous it was可知应与过去事实相反。
9. C。mustn’t表示“不准许”，may表示可能性，所以C正确。
10. C。句意：她或许到过那里，或者……。or ... 是重要的信息，说明还有其他的可能性。A的说法太绝对，与or ... 提供的信息冲突。
11. A。must表示的把握最大，may表示有可能，need不表示推测，will表示将来。根据句意可知A正确，表明对对方的不理解和责备，语气比较坚决。
12. C。shouldn’t have done 表示“本不该做……，但实际上却做了”。
13. A。疑问句中可以用can, 肯定句用must。
14. B。will + have done，表示对将来必然进程的猜测。
15. A。should 表示主观性猜测，译为“应该”。 16. C。can’t 表示否定的猜测，侧重于主观判断，译为“决不会；不可能”。
17. D。should表示劝告某人应该做某事。
18. A。need引导的一般疑问句，肯定回答应用must。
19. A。Shall I ... ？是征求对方意见时常用的句型。
（四）部分答案与解析
1. D. must表示推测时不用于否定句；shouldn’t have done sth. 表示“本不应该做某事而实际上做了”；needn’t have done sth. 表示“本来不必做某事而实际上做了”；couldn’t have done sth. 表示“不可能做过某事”。根据题意，选D。
2. A. 情态动词ought 后要接带to的不定式，ought to do 的否定式是ought not to do，所以答案是A。
3. A. must not always be doing sth. 表示“不要老是做谋事”，含有埋怨、指责、反感等感彩。
4. D. 题中的A项和B项都指现在情况；couldn’t have gone表示“不可能去过”；shouldn’t have gone表示“本不应该去而实际上去了”。根据题意，选D。
5. D. could have done sth. 表示“本来能够做某事而实际上未能做成”。
6. D. should可用于表示惊奇、感叹、不满等感彩的句子，如指过去的动作，则要用should have done sth. Would 和 may通常不带感彩。
7. C. 题中的dare是情态动词，后接不带to的不定式，主要用于疑问句、否定句和条件句中。
8. B. must开头的疑问句，否定答语用needn’t或don’t have to。
9. C. would rather通常也视为情态动词（组），后接动词原形，其否定形式为would rather not。
10. D. need作为情态动词，其否定形式为needn’t；作实义动词时，其否定形式为don’t (doesn’t) need to do。
11. D. must用在肯定句中表推测时，语气比could, would等肯定得多。此处“must + 不定式进行式”表“想必正在……”之意。
12. A. would rather … than …，意为“宁愿（做）……而不（做）……”。
13. B. 由句意可知，这是对过去发生的事情不太有把握的推测。
14. D. needn’t have done意为“过去不必做而做了某事”。
15. D. should have done表示“过去应该做而没有做某事”。
16. C. can’t（不能），mustn’t（不准），may not（不可以），均不合题意。
17. D. don’t have to = needn’t
18. D. will用在第二人称的疑问句中，为询问（或征求）对方的意愿或向对方提出请求之意。
19. B. should not have done表示“过去不应该做而做了某事”，含有“后悔”、 “责备”、 “劝告”， “批评”之意。
20. A. may开头的疑问句，否定答语常用mustn’t。
21. D. 疑问句中shall用于第一、三人称，用来征询对方的意见。
22. D. 推测“她不可能在会上发言”，must表示推测时，不能用于否定句中。
23. B. will在此处表示“意志（向）”。
24. D. should not have done表示“过去不应该做而做了某事”，含有“后悔”、 “责备”、 “劝告”， “批评”之意。
25. B. must do表示对现在的事实进行推测。
26. C. must have done用于对过去发生的事情进行推测，且较有把握。
27. C. 表示推测时，must比may语气肯定。
28. A. can表推测，只用于否定句和疑问句中。
29. D. must表示推测时，其后的反意问句有两种情况：①对现存状态（现在的事实）进行推测时，反意疑问句中动词用其一般现在形式。②对过去发生的事情进行推测时，若有表过去的时间状语，反意问句用动词的过去式。
30. C. needn’t have done表示“过去不必做而做了某事”，若表示“不必做某事（且实际上未做）“则用”didn’t / don’t / doesn’t need to.”
31. D. A表示“本能够”，B, C表“本应该”。
32. D. have to表示客观上要求做某事，must表示主观上认为必须做某事。
33. D. ought to的反意问句应用oughtn’t或shouldn’t开头。
34. C. should 含“按理应该做……”、“有义务做……”之意。
35. C. Let’s 中的us一般包括对方在内。
36. A. Let us中的us一般不包括对方在内。
37. D. may和shall均可表“允诺”。
38. A. 由句后得知句意为“我开始没听清楚对方的电话号码”，为对过去的事实或发生动作的表述。
39. C. used to do“过去（常）做某事”，be used to doing“习惯于做某事”。
40. D. would rather后接动词原形。Spend … on sth.为常用结构。
（一）情态动词的定义 ：情态动词表示说话人对某一动作或状态的态度。
（二）情态动词的特点 ：1）有一定词义；2）不受主语人称和数的变化影响；3）与主要动词的原形（或称不带to的不定式）一起构成谓语（除ought to作固定词组看待）。
情态动词无人称和数的变化, 情态动词后面跟的动词需用原形,否定式构成是在情态动词后面加 "not"。 个别情态动词有现在式和过去式两种形式, 过去式用来表达更加客气, 委婉的语气, 时态性不强, 可用于过去，现在或将来。情态动词属非及物动词，故没有被动语态。
He could be here soon. 他很快就来。 We can't carry the heavy box. 我们搬不动那箱子。
I'm sorry I can't help you. 对不起，我帮不上你。
基本助动词与情态助动词最主要的区别之一是，基本助动词本身没有词义，而情态助动词则有自己的词义，能表示说话人对有关动作或状态的看法，或表示主观设想：
What have you been doing since （构成完成进行体，本身无词义）
I am afraid I must be going. （一定要）
You may have read some account of the matter. （或许已经）
除此之外，情态助动词还有如下词法和句法特征：
1） 除ought和used以外，其他情态动词后面只能接不带to的不定式。如果我们把ought to和used to看做是固定词组的话，那么，所有情态动词无一例外地只能接不带to的不定式：
We used to grow beautiful roses.
I asked if he would come and repair my television set.
2） 情态助动词在限定动词词组总是位居第一： They need not have been punished so severely.
3） 情态助动词用于第三人称单数现在时的时候，没有词形变化，即其词尾无-s形式：
She dare not say what she thinks.
4） 情态动词没有非限定形式，即没有不定式和分词形式，也没有相应的动名词：
Still, she needn't have run away.
5） 情态助动词的“时”的形式并不是时间区别的主要标志。在不少场合，情态助动词的现在时和过去时形式都可以表示现在、过去或将来时间： Would you mind very much if I ask you to do something She told him he ought not to have done it.
6） 情态助动词之间是相互排斥的，即在一个限定动词词组中只能出现一个情态助动词，但有时却可以与have和be基本助动词连用： You should have washed the wound.
Well, you shouldn't be reading a novel.
（三）情态动词有四类：①只做情态动词：must,can(could),may(might),ought to ②可做情态动词又可做实义动词：need,dare ③可做情态动词又可做助动词：shall(should),will(would)
④具有情态动词特征：have(had,has) to,used to ⑤情态动词表猜测
（四）情态动词的基本用法
1. can (could)
1）表示能力，could主要指过去时间。
Two eyes can see more than one. 两只眼比一只眼看得清。
Could the girl read before she went to school 这女孩上学前能识字吗？
2）表示可能（理论上或是逻辑判断上）。
The temperature can fall to –60℃, that is 60℃ below freezing.
气温可降至—60℃，也就是零下60℃。
He can t (couldn t) have enough money for a new car. 他不可能有足够的钱买新车。
You mustn t smoke while you re walking around in the wood. You could start a fire.
在林子里走时勿吸烟，那样可能会引起火灾。
3）表示允许。
Can I have a look at your new pen 我可以看一看你的新钢笔吗？
He asked whether he could take the book out of the reading—room.
他问他可不可以把书带出阅览室。
4）表惊异、怀疑、不相信等态度。主要用于否定句、疑问句或感叹句中。
Where can (could) they have gone to 他们会去哪儿了呢？
He can t (couldn t) be over sixty. 他不可能超过六十岁。
How can you be so careless 你怎么这么粗心？
5）比较委婉客气地提出问题或陈述看法。
Can (Could) you lend me a hand 帮我一把好吗？
I m afraid we couldn t give you an answer today. 恐怕我们今天不能给你答复。
2. may (might)
1）表允许，might可以指过去时间，也可指现在时间，语气更委婉。
You may take whatever you like. 你喜欢什么就拿什么。
He told me that I might smoke in the room. 他告诉我可以在房间里抽烟。
May (Might) I ask for a photo of your baby 我可以要一张你宝宝的照片吗？
在回答以may引起的问句时，多避免用这个词，而用其它方式，如Yes, please. / Certainly.
/ Please don t ./ You d better not. / No, you mustn t.等，以免显得太严峻或不客气。
2）表可能（事实上）。可以指过去时间，也可以指现在时间，但语气更加不肯定。
He may be at home. 他可能在家。
She may not know about it. 她可能不知道这件事。
He was afraid they might not agree with him. 他担心他们可能不同意他的意见。
They might be having a meeting, but I m not sure. 他们有可能在开会，不过我不肯定。
3. must
1）表示义务。意为“必须”（主观意志）。
We must do everything step by step. 我们一切都必须循序渐进地做。
You mustn t talk to her like that. 你不可能那样对她说话。
--Must we hand in our exercise—books now 我们现在就要交练习本吗？
--No, you needn t. / No, you don t have to. 不必。（这种情况下，一般不用mustn t）
2）表示揣测。意为“想必、准是、一定”等，只用于肯定句。
He must be ill. He looks so pale. 他准是病了。他的脸色苍白。
She s wearing a diamond necklace. She must have a lot of money.
她戴着钻石项链，一定很有钱。
4. shall
1）表征询意见，用于第一、第三人称疑问句。
Shall I get you some tea 我给你点茶好吗？
Shall the boy wait outside 让那男孩在外面等吗？
What shall we do this evening 我们今晚做什么？
2）表说话人的意愿，有“命令、允诺、警告、决心”等意思，用于第二、第三人称陈述句。
You shall do as I say. 按我说的做。（命令）
You shall have my answer tomorrow. 你明天可以得到我的答复。（允诺）
He shall be sorry for it one day, I tell you. 有一天他会后悔的，我告诉你。（警告）
Nothing shall stop us from carrying out the plan. 什么也不能阻止我们执行这项计划（决心）
5. will
1）表意愿，用于各种人称陈述句。
I will do anything for you. 我愿为你做任何事。
None is so blind as those who won t see. 不愿看的人眼最瞎。
If you will read the book, I ll lend it to you. 如果你愿意读这本书，我会把它借给你。
2）表请求，用于疑问句。
Will you close the window It s a bit cold. 请你把窗户关上好吗？有点冷。
Won t you drink some more coffee 再来一点咖啡好吗？
3）表示某种倾向或习惯性动作。
Fish will die out of water. 鱼离开水就不能活。 The door won t open. 这门打不开。
The boy will sit there hour after hour looking at the traffic go by.
那男孩常常坐在那里好几个钟点，看着车辆行人通过。
6. should
1）表义务。意为“应该”（某件事宜于做），用于各种人称。
You should be polite to your teachers. 你对老师应该有礼貌。
You shouldn t waste any time. 你不应该浪费时间。
2）表推测，意为“想必一定、照说应该、估计”等。
The film should be very good as it is starring first—class actors.
这部新电影是一流演员主演的，估计拍得很好。
They should be home by now. 照说他们现在应当已经到家了。
7.would
1）表意愿。
They would not let him in because he was poorly dressed. 他们不让他进去因为他衣着旧。
I said I would do anything for you. 我说过我愿意为你做任何事。
2）表委婉地提出请求、建议或看法。
Would you like another glass of beer 再来杯啤酒好吗？
Would you mind cleaning the window 请把窗户擦一下好吗？
They wouldn t have anything against it. 他们不会有什么反对意见。
3）表过去反复发生的动作或过去的一种倾向。
Every time she was in trouble, she would go to him for help.
她每遇到麻烦都会向她求助。他告诉我盒子打不开了。
8. ought to
1）表义务，意为“应该”（因责任、义务等该做），口气比should稍重。
You are his father. You ought to take care of him. 你是他父亲，应当管他。
You oughtn t to smoke so much. 你不应该抽这么多烟。
2）表推测，暗含很大的可能，语气较弱。
Han Mei ought to know his telephone number. 韩梅该知道他的电话号码。
There s a fine sunset; it ought to be a fine day tomorrow. 今天有晚霞，明天应该是个好天。
9. used to
表示过去的习惯动作或状态，现在不复发生或存在。疑问式和否定式有两种。
He used to live in the countryside, but now he lives in the city.他过去住在乡下，现在住在城里。
There used to be a building at the street corner, but it has been pulled down.
街道拐角处过去有座楼房，现在拆了。
I usedn t (didn t use) to smoke. 我过去不抽烟。
Used you (Did you use) to go to school on foot 你过去常步行去学校吗？
（五）其他用法
首先它是动词，而且不同于行为动词，行为动词表示的是可以通过行为来表达的动作（如写，读，跑），而情态动词只是表达的一种想法（如能，也许，敢）。
用法是：情态动词+行为动词原形
例句：I can read this sentence in English. 我能用英语读这句话。
情态动词是一种本身有一定的词义,表示说话人的情绪,态度或语气的动词,但不能单独作谓语, 只能和其他动词原形构成谓语。
We can be there on time tomorrow.我们明天能按时去那儿。
May I have your name 我能知道你的名字吗？
Shall we begin now 我们现在就开始吗？
You must obey the school rules.你必须遵守校规。
情态动词数量不多,但用途广泛,主要有下列: can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would),have (to) ,had better.
情态动词还有一个很重要的用法，即情态动词表推测——
情态动词表推测的用法小结
（一）情态动词表推测的三种句式
1.在肯定句中一般用must (一定)，may（可能），might / could（也许，或许）。
（1）He must/may/might know the answer to this question
他一定/可能/也许知道这个问题的答案。
（2）It is cold in the room. They must have turned off the heating.
屋里很冷，他们肯定把暖气关了。
2.否定句中用can’t / couldn’t(不可能), may not/might not(可能不)。
（1）It can’t/couldn’t be the headmaster. He has gone to America.
这不可能是校长，他去美国了。
（2）He may not/might not know the scientist. 他也许不认识那位科学家。
3.疑问句中用can/could (能…… )。
（1）Could he have finished the task 他可能把任务完成了吗？
（2）Can he be at home now 他现在能在家吗？
注：以上三种句式中情态动词的语气按程度都是依次递减的。Might, could并非may, can的过去式，而表示语气较为委婉或可能性较小。
（二）情态动词表推测的三种时态
1.对将来情况的推测，用“情态动词 + 动词原形”。
（1）She must / may / might / could arrive before 5. 5:00前她一定/可能/也许到。
（2）She must/may/might/could walk miles and miles among the hills without meeting anyone.
她一定/可能/也许会在山里一连走好几英里而遇不到一个人。
2.对现在或一般情况的推测，用“情态动词 + be”，“情态动词 +be doing”或“情态动词 + 动词原形”。
（1）He must / may / might / could be listening to the radio now.
他一定/可能/也许正在听收音机。
（2）He can’t ( couldn’t ) / may ( might ) not be at home at this time.
这个时候他不可能/可能不在家。
（3）Mr. Bush is on time for everything .How can ( could ) he be late for the opening ceremony
布什先生一向准时，这次开幕式他怎么可能迟到呢？
3.对过去情况的推测，用“情态动词 + have +过去分词”。
（1）It must / may / might / could have rained last night .The ground is wet.
地湿了，昨晚肯定/可能/也许下雨了。
（2）The door was locked. He can ( could ) not / may ( might ) not have been at home .
门锁着，他不可能/可能不在家。
（3）Can / Could he have gotten the book？
难道他找到书了吗？
注：情态动词 should /ought to表推测时，意为“想必会，理应……”但与“have +过去分词”连用时，则又可构成虚拟语气意为“本应该做某事却没做”。例如：
（4）It’s seven o’clock. Jack should/ought to be here at any moment.
现在七点钟了，杰克理应随时到达。（推测）
（5）She should / ought to have attended your birthday party, but she had to look after her mother in hospital. （虚拟） 她本该出席你的生日晚会的，可是她得在医院照顾她妈妈。
（6）Tom should not /ought not to have told me your secret, but he meant no harm. （虚拟） 汤姆本不该告诉我你的秘密，可是他并无恶意。
（六）功能
助动词(auxiliary)主要有两类：基本助动词(primary auxiliary)和情态助动词(modal auxiliary)。基本助动词有三个：do, have和be；情态助动词基本的有十四个：may, might; can, could; will, would; shall, should; must, need, dare, used to, ought to.had better 上述两类助动词的共同特征是，在协助主动词构成限定动词词组时，具有作用词的功能：
1） 构成否定式：
He didn't go and neither did she. The meeting might not start until 5 o'clock.
2） 构成疑问式或附加疑问式：
Must you leave right now You have been learning French for 5 years, haven't you
3） 构成修辞倒装：
Nowhere can he obtain any information about his sister.
Hardly had he arrived when she started complaining.
4） 代替限定动词词组：
A: Who can solve this crossword puzzle B: Tom can.
A: Shall I write to him B: Yes, do.
重点疑难
（一）need和dare的用法
need和dare既可用作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句和疑问句。用作实义动词时，可用于各种句式。
1.用作情态动词
--Need I come --Yes, you must. --我需要来吗？ --需要。
You needn t telephone him now. 你现在不必打电话给他。
I don t think you need worry. 我想你不必发愁。
She dare not go out alone at night. 她晚上不敢一个人出去。
How dare you say I m unfair 你竟敢说我不公平？
Not one of them dared mention this. 他们谁也不敢提这件事。
2.用作实义动词
You don t need to do it yourself. 你不必亲自做这件事。
We need to tell them the news. 我们需要把这消息告诉他们。
The table needs painting (to be painted.). 桌子需要油漆一下。
We should dare to give our own opinion. 我们要敢于提出自己的观点。
He did not dare (to) look up. 他不敢抬头看。
I dare day he ll come again. 我想他会再来的。 （cI dare say…为固定习语）
（二）情态动词后跟完成式和进行式的用法
1.情态动词后跟完成式，表“应当已经……”，“想必已经……”，“本来可以……”等意。
I should have finished the work earlier. 我应当早一点完成这项工作的。
He isn t here. He must have missed the train. 他还未到，一定是没赶上火车。
Where can (could) he have gone 他能到那里去了呢？
You may (might) have read about it. 你可能在报上已经读到这件事了。
You could (might) have been more careful. 你本来可以更细心的。
He needn t have worried about it. 他本不必为此事担心。
There was a lot of fun at yesterday s party. You ought to have come, but why didn t you
昨天的聚会非常有意思。你本应该来，为何不来呢？
2. 情态动词后跟进行式，表示“想必正在……”，“可能正在……”，“应当正在”等意。
It s twelve o clock. They must be having lunch. 现在是十二点。他们一定正在吃饭。
They may be discussing this problem. 他们可能正在论讨这个问题。
He can t be telling the truth. 他说的不可能是真话。
She shouldn t be working like that. She s still so weak. 她不应当那样干，她身体仍那么虚。
（三）几组词的辨异
1. can 和be able to
1）情态动词can只有两种时态形式，现在式can和过去式could，而be able to有多种时态形式。
Mary can play the piano. She has been able to play it since she was 5.
玛丽会弹钢琴。她五岁起就会弹了。
2）用在过去时中，could经常表示能够做某事，事实上不一定去做，而was∕were able to则表示“过去做成了某事”。在否定句中两者可通用。
He could swim across the English Channel. But he didn t feel like it that day.
他能游过英吉利海峡，但那天他不想游。
Yesterday I was able to get home before the heavy rain. 昨天我在下大雨前赶到了家里。
2. must和 have to
must表示主观意志，而have to表示由于客观因素不得不做某事。must没有过去式，除在间接引语中可用于表示过去时间，在直接引语中表示过去时间应该用had to代替。
I told her that she must give up smoking. 我叫她必须戒烟。
We had to get everything ready that night. 我们那晚得把一切准备就绪。
3. would和used to
1）used to表示过去与现在或过去某时与后来的情况有不同，而would只表过去的情况。People used to think that the earth was flat.
过去人们认为地球是平的。（现在人们不这么认为。）
She would go out for a walk in the morning when she was in the country.
在乡下时，她总是在早晨去散会儿步。（可能现在仍有散步的习惯。）
2）used to可表示过去的习惯动作和经常的情况，而would只表示过去的习惯动作。
He used to ∕would smoke while writing. 过去他写东西时常抽烟。
She used to be fat. 她过去很胖
专项练习（一）
1. I __________ you, because I thought I must be wrong.
A. dare not ask B. dare not to ask C. dare not asking D. dare to not ask
2. There __________ some flowers in the garden.
A. were used to be B. used to be C. uses to be D. used to be having
3. “__________ I take it out ” “I m sorry, you __________.”
A. Could …couldn t B. Might…might not C. Could…can D. May…can t
4. You were stupid to climb the tree. You __________ hurt yourself.
A. may B. might C. will D. might have
5. You __________ those letters. Why didn t you
A. should post B. should have posted C. must have posted D. ought to post.
6. All the lights are on, the Smiths __________ up.
A. must get B. is getting C. must be getting D. would get
7. He __________ lead a horse to the water but he __________ not make it drink.
A. will…can B. may…can C. may…dares D. dare…can
8. “Need we do this job now ” “Yes, __________.”
A. you need B. you should C. you must D. you can
9. __________ to have lunch with us today
A. Do you likes B. Would you like C. Will you liked D. Have you liked
10. He said that you __________ watch TV all the evening if you wished.
A. may B. must C. can D. might
11. –Is John coming by train --He should, but he __________ not. He likes driving his car.
A. must B. can C. need D. may
12. Peter __________ come with us tonight, but he isn t very sure yet.
A. must B. can C. may D. will
13. Michael __________ be a policeman, for he s much too short.
A. needn t B. can t C. shouldn t D. won t
14. I thought you __________ be hungry, so I have brought you some cakes.
A. may B. might C. can D. could
15. I wonder how he __________ that to the teacher.
A. dare to say B. dare saying C. not dare say D. dared say
e on! We __________ hurry because there isn t much time left.
A. may B. must C. can D. need
17. Amy did best in the English test. She __________ hard last week.
A. must have working B. should have worked C. should work D. must work
18. The fire spread through the hotel very quickly but everyone __________ get out.
A. had to B. would C. could D. was able to
19. –--I stayed at a hotel while in New York. ---Oh, did you You __________ with Barbara.
A. could have stayed B. could stay C. would stay D. must have stayed
20. It s nearly seven o clock. Jack __________ be here at any moment.
A. must B. need C. should D. can
答案： 1.A2.B3.D4.D5.B6.C7.B8.C9.B10.D11.D12.C13.B14.B15.D16.B17.A18.D19.A20.
专项练习（二）
1. Jean have kept his promise. I wonder why he changed his idea.
A. must B. should C. need D. would
2. Jane have come to the party, but she not find the exact time.
A. could; could B. might; could C. should; could D. should; would
3. So many mistakes in your homework! You more careful.
A. may be B. had to C. would be D. should have been
4．Her brother be at home now, because he was seen playing basketball in the stadium just now. A. mustn’t B. needn’t C. can’t D. shouldn't
5．---I can’t understand why our boss is late. ---He the early bus.
A. could miss B. may have missed C. can have missed D. might miss
6. She didn't answer the phone, she ______ asleep.
A. may be B. must be C. should have been D. must have been
7．The little girl’s eyes were red. She ______.
A. may cry B. must cry C. must be cried D. must have been crying
8．He______ his supper now, for the dining hall is still closed.
A. can’t be having B. needn’t be having C. mustn’t be having D. shouldn't be having
9．I parked my bike behind the building, but now it is gone. It ________ .
A. may be stolen B. must be stolen C. must have been stolen D. must have stolen
10. ______ Mr. Black_______go to work by ferry before the bridge was built
A. Did; used to B. Use; to C. Did; use to D. Does; use to
11. The hotel is only a stone’s throw away, you ______ take a bus.
A. need not to B. not need to C. don't need D. need not
12. I am busy now, _______ my brother do it for you
A. Will B. Shall C. Must D. May
13. ---You needn’t do it right now, need you ---Yes I am afraid I ______ .
A. need B. needn’t C. must D. mustn’t
14.My English-Chinese dictionary has disappeared . Who _____ have taken it (2003年上海春季高考) A. should B. must C. could D. would
15. ---The room is so dirty._______ we clean it ----Of course. (2003年北京春季高考)
A． Will B. Shall C. Would D. Do
16. If you have something important to do, you ______ waste any time.
A. needn’t B. mustn’t C. may not D. won’t
17. If you want to borrow a football after school, your student card______ here.
A. has to leave B. must leave C. has to be left D. must be left
18. “ Did you scold him for his carelessness ” “Yes, but _____ it”
A. I’d rather not do B. I’d rather not have done C. I shouldn’t do D. I’d better not do
19. “ Don’t get near to it . It is too dangerous!” “_______” .
A. Yes, I won’t B. No, I don’t C. No, I can’t D. No, I won’t
20. He must be in the classroom, _______ he
A. mustn’t B. can’t C. isn’t D.can
21. He________ be in the garden. He must be in the room.
A. can’t B. mustn’t C. will not D. may not
22. “Do you have to leave now ” “I am very sorry, but I really______.”
A. can’t B. have C. should D. must
23. “Let’s go to the library, shall we ” “_________ ”
A. No, I can’t B. Yes, I will C. Yes , thank you D. No, we’d better not
24. “Can I take it away ” “ You ______ better not.”
A. should B. could C. would D. had
25. You _______ have brought your camera. They all had theirs with them.
A. couldn’t B. needn’t C. wouldn’t D. mustn’t
26. See who is there!______it be May
A. May B. Must C. Can D. Will
27. John______ be a basketball player. He is much too short.
A. may B. mustn’t C. can’t D. should
28. The Chinese teacher looks so pale. She ______ be ill.
A. must B. mustn’t C. can D. need
29. Something______to save our earth. Do you think so
A. can do B. must do C. has to do D. must be done
30. Look at what you have done! You ______ be more careful.
A. ought B. can C. would D. should
专项练习（三）
1. — Has Li Lin started He said he would join in the party.
— He ______. He is a man of keeping his word.
A. could have left B. must have left C. can’t come D. won’t be coming
2. — May I park my car here — No, you ______. No car is allowed to park here.
A. may not B. needn’t C. mustn’t D. daren’t
3. — Excuse me, could you tell me where the Yajia Supermarket is
— It’s two blocks straight ahead. You ______ miss it.
A. mustn’t B. can’t C. needn’t D. shouldn’t
4. — I saw Mr. Sun at Tongyu Station this morning.
— You ______. He’s still on holiday in Hawaii.
A. couldn’t have B. mustn’t have C. shouldn’t D. needn’t
5. — How about paying a visit to Dr. Wang, our former Chinese teacher
— Good idea. I will e-mail him today so that he ______ know ______ to expect us.
A. shall; why B. could; when C. would; what D. will; how
6. Everything has two sides. Beautiful songs, sometimes, ______ be just noise to others.
A. must B. may C. should D. could
7. Someone ______ my umbrella. I found it wet yesterday.
A. must be using B. must have used C. must use D. must have been using
8. — How dangerous it was!— Yes, but for the passer-by’s quick action, the girl ______.
A. was drowned B. could have been drowned C. had drowned D. should be drowned
9. You ____ scold such a pupil who always keeps silent so seriously that you _____ hurt him.
A. should; can B. may; will C. mustn’t; may D. can’t; must
10. — Why does Alice know so much about Angkor Wat — She ______ have been there, or ...
A. must B. oughtn’t to C. may D. can’t
11. — You may laugh, but I’ve been thinking of becoming a vegetarian.— Oh, you ______ be crazy. You will be hungry all the time.
A. must B. may C. will D. need
12. — What’s the matter with you
— Oh, I’m not feeling well in the stomach. I ______ so much fried fish just now.
A. shouldn’t eat B. mustn’t have eaten C. shouldn’t have eaten D. mustn’t eat
13. — ______ he have been chosen as captain of the football team — Yes, he ______.
A. Can; must have B. Must; must have C. Can; must D. Must; must
14. Mr. Zhang ______ in Shanghai tomorrow morning.
A. can have arrived B. will have arrived C. may have arrived D. must have arrived
15. Miss Wang started at 8 o’clock, and she ______ be there now.
A. should B. can C. can’t D. need
16. — It must be Mr. Li who did it. — No, it ______ be Mr. Li.
A. mustn’t B. wouldn’t C. can’t D. may
17. You ______ finish reading the book as soon as possible.
A. may B. can C. need D. should
18. — Need you go to work now — Yes, I ______.
A. must B. need C. can D. dare
19. Your trousers are dirty. ______ them for you
A. Shall I wash B. Will I wash C. Am I going to wash D. Am I washing
20. You are late for school today. You ______ to school earlier.
A. ought to come B. should have come C. ought have come D. should come
21. We must learn from Lei Feng, ______ we
A. may B. can’t C. don’t D. needn’t
22. She must be hungry, ______ she
A. isn’t B. needn’t C. doesn’t D won’t
23. He ought to come here early, ______ he
A. would B. should C. didn’t D. shouldn’t
24. You used to smoke, ______ you
A. used to B. don’t C. didn’t D. shouldn’t
25. You ought ______ for what you haven’t done.
A. not to be punished B. not be punished C. to not punished D. to not be punished
26. ______ you please tell me the way to the post office
A. Must B. Need C. Would D. Should
27. I’m sure he ______ have the computer sooner or later.
A. shall B. can C. must D. would
28. It is important that we ______ learn how to drive.
A. have to B. should C. need D. shall
专项练习（四）
1. I didn’t see her in the meeting room this morning. She _____ at the meeting.
A. mustn’t have spoken B. shouldn’t have spoken
C. needn’t have spoken D. couldn’t have spoken
2. One ought _____ for what one hasn’t done.
A. not to be punished B. to not be punished
C. to not punished D. not be punished
3. If you really want yourself to be in good health, you must ___ always ___ so much.
A. not; be smoking B. not; have smoked
C. not; to smoke D. be not; smoking
4. With so much work on hand, you _____ to see the game last night.
A. mustn’t go B. shouldn’t go
C. couldn’t have gone D. shouldn’t have gone
5. Most of the students felt rather disappointed at the English party. They say that it ______ better organized.
A. had been B. had to be C. must have been D. could have been
6. I’m surprised that he _____ in the exam.
A. should fail B. would have failed
C. may have failed D. should have failed
7. The little girl _____ there alone.
A. not dare go B. dares not go C. dare not go D. dare not to go
8. “Must we do it now ” “No, you _____.”
A. won’t B. needn’t C. can’t D. don’t
9. He said he would rather not _____ it right now.
A. doing B. to do C. do D. to be doing
10. You _____ to the meeting this afternoon if you have something important to do.
A. needn’t to come B. don’t need come
C. don’t need coming D. needn’t come
11. Put on more clothes. You _____ be feeling cold with only a shirt on.
A. can B. could C. would D. must
12. I _____ play football than baseball.
A. would rather B. had better C. like better D. prefer
13. I thought you _____ like something to read, so I have brought you some books.
A. may B. might C. could D. must
14. There was plenty of times. She _____.
A. mustn’t have hurried B. couldn’t have hurried
C. must not hurry D. needn’t have hurried
15. The plant is dead. I _____ it more water.
A. will give B. would have given
C. must give D. should have given
16. You _____ return the book now. You can keep it till next week if you like.
A. can’t B. mustn’t C. needn’t D. may not
17. It’s still early, you _____.
A. mustn’t hurry B. wouldn’t hurry
C. may not hurry D. don’t have to hurry
18. Please open the window, _____
A. can’t you B. aren’t you C. do you D. will you
19. We _____ for her because she never came.
A. mustn’t have waited B. shouldn’t have waited
C. mustn’t wait D. needn’t wait
20. — May I stop here — No, you _____.
A. mustn’t B. might not C. needn’t D. won’t
21. It’s a fine day. Let’s go fishing, _____.
A. won’t we B. will we C. don’t we D. shall we
22. I didn’t see her in the meeting room this morning. She _____ at the meeting.
A. mustn’t have spoken B. shouldn’t have spoken
C. needn’t have spoken D. couldn’t have spoken
23. — Please don’t make a noise. — _____. I’ll be as quiet as a mouse.
A. Yes, I won’t B. No, I won’t C. No, I will D. Yes, I will
24. The young man has made so much noise that he _____ not have been allowed to attend the concert.
A. could B. must C. would D. should
25. — Where is John — He _____ in the library.
A. should be B. must be C. can be D. must have been
26. Since the road is wet this morning, _____ last night.
A. it must rain B. it must be raining
C. it must have rained D. it must have been rain
27. — Will your brother stay home tonight
— I’m not quite sure. He _____ to the cinema tonight.
A. must go B. can go C. may go D. may be going
28. She’s already two hours late. What ______ to her
A. can have happened B. may have happened
C. should have happened D. must happen
29. You must be a writer, _____
A. mustn’t you B. are you C. must you D. aren’t you
30. I got up early that morning, but I _____ so because I had no work to do.
A. mustn’t have done B. didn’t need to do
C. needn’t have done D. can’t have done
31. He _____ have come here yesterday, but he didn’t.
A. could B. should C. ought to D. all the above
32. I missed the last bus, so I _____ go home on foot.
A. must B. have to C. may D. had to
33. He ought to win the first prize, _____ he
A. oughtn’t B. shouldn’t C. mustn’t D. both A and B
34. Everyone _____ do his best for the modernizations of our country.
A. can B. may C. should D. might
35. Let’s clean our classroom, _____
A. will you B. don’t we C. shall we D. do you
36. Let us play basketball, ______
A. will you B. don’t we C. shall we D. do you
37. He asked me for this book many times. Please tell him that he _____ have it tomorrow.
A. must B. may C. shall D. both B and C
38. “Your phone number again I _____ quite catch it.” “It’s 9568442.”
A. didn’t B. couldn’t C. don’t D. can’t
39. Mother _____ us stories when we were children.
A. was used to tell B. is used to telling C. used to tell D. used to telling
40. She would rather _____ more money on books _____ on clothes.
A. cost … not B. to spare … don’t C. pay … than D. spend … than
专项练习（二）
1.解析：选B. “should have +过去分词” 表示“过去本来应该(但没能)做某事”；keep one’s promise 意为“信守诺言”。
2.解析：选A.“ could have+过去分词表示过去本来应该(但没能)做某事”。
3.解析：选D. “You should have been more careful”. 意为：你本来应该更细心的。
4．解析：选C. can’t be at home 意为：不可能在家。
5解析：选B. “may have+过去分词”表示对过去动作的判断，意为：可能做了某事。 注意：can表示可能时，只能用于疑问句和反问句。
6.解析：选D. 表示：对过去发生的事情的肯定推测。
7．解析：选D. 意为：她刚才肯定一直在哭。对过去某事正发生的推测。
8．解析：选A. 对现在正在发生的事情的否定推测。
9．解析：选C. 对过去发生的事情 的肯定推测的被动式。
10.解析：选C. used to do的疑问式，可以是Used+主语+to do 或Did +主语+use to do
11.解析：选D. 说话人认为不必要乘车, need 为情态动词。
12.解析：选B. 在疑问句中shall 用于第三人称，也表示征求意见。
13.解析：选C. Yes的意思是：不。意为：恐怕我必须现在就做。
14.解析：选C. could/can have done 用于否定推测和疑问推测。
15.解析：选B. shall 用在疑问句中，常用于第一，三人称， 表示征求意见或请求指示。
16.解析：选B. 根据句意用mustn’t
17.解析：选C. have to 表示客观需要，must表示主观需要。学生证必须放在此是客观需要。
18.解析：选B. would rather 加完成时表示对完成了的或过去了的事情的态度。意为：当时是不情愿做的。
19.解析：选D. A为错误的表达方式；B和C没有直接回答对方的问候。
20.解析：选C. 对表否定的must进行反意疑问时，要用句子的实义动词
21.解析：选A. 否定推测用can’t不用mustn’t
22.解析：选D. 回答have to 的疑问句用must作肯定回答。
23.解析：选D. A,B,C都 不能回答shall we, 此处D的语气比较婉转客气。
24.解析：选D. had better 与不带to 的不定式构成谓语，可以变成疑问句：Hadn’t you better----
25. 解析：选B. 本来不必要做某事.
26. l解析：选C. 表推测时A，B都用作疑问句。
27.解析：选C. 断然的不定推测用can’t
28.解析：选A. 表示有把握的肯定推测用must
29.解析：选D. “something must be done” 意为：必须采取措施。
30. 解析：选D. ought 后应用to
（三）答案及解析：
1. B。从He is a man of keeping his word中可以看出，李林肯定已经出发来参加聚会了，这是对已经发生的事情非常肯定的推测，故用must have done。注意must表推测时，不能用于否定句和疑问句中。
2. C。此题考查以情态动词提问的一般疑问句的回答。在英语中，以某些情态动词提问的句子，出于礼貌委婉或句意的需 要，回答时，要换用另一个情态动词。在回答must开头的一般疑问句时，肯定回答用must，否定回答用needn’t或don’t have to；在回答may开头的一般疑问句时，肯定回答用may，否定回答用mustn’t；在回答need开头的一般疑问句时，肯定回答用must，否定回答用needn’t。
3. B。根据题意，此处需要表示“推测”的否定结构，故can’t为正确答案。4. A。这是一个省略句，couldn’t have done表示对过去发生的动作的否定推测，意为“不可能……”。
5. B。这是一个综合题。本题so that后的目的状语从句中的谓语动词要用“情态动词（ may / might / can / could ） + 动词原形”。When to expect us表示“我们什么时候可到达”。“疑问词+不定式”结构在句中作know的宾语。
6. B。由sometimes可知，此处应用表示可能性不大的情态动词，即may。
7. B。由后句可知，这是对过去发生的事情的肯定推测，故B项正确。
8. B。but for的意思是“要不是”，语法功能上等同于if 引导的否定虚拟条件句，因前句中How dangerous it was可知应与过去事实相反。
9. C。mustn’t表示“不准许”，may表示可能性，所以C正确。
10. C。句意：她或许到过那里，或者……。or ... 是重要的信息，说明还有其他的可能性。A的说法太绝对，与or ... 提供的信息冲突。
11. A。must表示的把握最大，may表示有可能，need不表示推测，will表示将来。根据句意可知A正确，表明对对方的不理解和责备，语气比较坚决。
12. C。shouldn’t have done 表示“本不该做……，但实际上却做了”。
13. A。疑问句中可以用can, 肯定句用must。
14. B。will + have done，表示对将来必然进程的猜测。
15. A。should 表示主观性猜测，译为“应该”。 16. C。can’t 表示否定的猜测，侧重于主观判断，译为“决不会；不可能”。
17. D。should表示劝告某人应该做某事。
18. A。need引导的一般疑问句，肯定回答应用must。
19. A。Shall I ... ？是征求对方意见时常用的句型。
（四）部分答案与解析
1. D. must表示推测时不用于否定句；shouldn’t have done sth. 表示“本不应该做某事而实际上做了”；needn’t have done sth. 表示“本来不必做某事而实际上做了”；couldn’t have done sth. 表示“不可能做过某事”。根据题意，选D。
2. A. 情态动词ought 后要接带to的不定式，ought to do 的否定式是ought not to do，所以答案是A。
3. A. must not always be doing sth. 表示“不要老是做谋事”，含有埋怨、指责、反感等感彩。
4. D. 题中的A项和B项都指现在情况；couldn’t have gone表示“不可能去过”；shouldn’t have gone表示“本不应该去而实际上去了”。根据题意，选D。
5. D. could have done sth. 表示“本来能够做某事而实际上未能做成”。
6. D. should可用于表示惊奇、感叹、不满等感彩的句子，如指过去的动作，则要用should have done sth. Would 和 may通常不带感彩。
7. C. 题中的dare是情态动词，后接不带to的不定式，主要用于疑问句、否定句和条件句中。
8. B. must开头的疑问句，否定答语用needn’t或don’t have to。
9. C. would rather通常也视为情态动词（组），后接动词原形，其否定形式为would rather not。
10. D. need作为情态动词，其否定形式为needn’t；作实义动词时，其否定形式为don’t (doesn’t) need to do。
11. D. must用在肯定句中表推测时，语气比could, would等肯定得多。此处“must + 不定式进行式”表“想必正在……”之意。
12. A. would rather … than …，意为“宁愿（做）……而不（做）……”。
13. B. 由句意可知，这是对过去发生的事情不太有把握的推测。
14. D. needn’t have done意为“过去不必做而做了某事”。
15. D. should have done表示“过去应该做而没有做某事”。
16. C. can’t（不能），mustn’t（不准），may not（不可以），均不合题意。
17. D. don’t have to = needn’t
18. D. will用在第二人称的疑问句中，为询问（或征求）对方的意愿或向对方提出请求之意。
19. B. should not have done表示“过去不应该做而做了某事”，含有“后悔”、 “责备”、 “劝告”， “批评”之意。
20. A. may开头的疑问句，否定答语常用mustn’t。
21. D. 疑问句中shall用于第一、三人称，用来征询对方的意见。
22. D. 推测“她不可能在会上发言”，must表示推测时，不能用于否定句中。
23. B. will在此处表示“意志（向）”。
24. D. should not have done表示“过去不应该做而做了某事”，含有“后悔”、 “责备”、 “劝告”， “批评”之意。
25. B. must do表示对现在的事实进行推测。
26. C. must have done用于对过去发生的事情进行推测，且较有把握。
27. C. 表示推测时，must比may语气肯定。
28. A. can表推测，只用于否定句和疑问句中。
29. D. must表示推测时，其后的反意问句有两种情况：①对现存状态（现在的事实）进行推测时，反意疑问句中动词用其一般现在形式。②对过去发生的事情进行推测时，若有表过去的时间状语，反意问句用动词的过去式。
30. C. needn’t have done表示“过去不必做而做了某事”，若表示“不必做某事（且实际上未做）“则用”didn’t / don’t / doesn’t need to.”
31. D. A表示“本能够”，B, C表“本应该”。
32. D. have to表示客观上要求做某事，must表示主观上认为必须做某事。
33. D. ought to的反意问句应用oughtn’t或shouldn’t开头。
34. C. should 含“按理应该做……”、“有义务做……”之意。
35. C. Let’s 中的us一般包括对方在内。
36. A. Let us中的us一般不包括对方在内。
37. D. may和shall均可表“允诺”。
38. A. 由句后得知句意为“我开始没听清楚对方的电话号码”，为对过去的事实或发生动作的表述。
39. C. used to do“过去（常）做某事”，be used to doing“习惯于做某事”。
40. D. would rather后接动词原形。Spend … on sth.为常用结构。