(共55张PPT)
第二节 情态动词和虚拟语气
第一讲
1.常见情态动词的用法
考点精析
考点1 情态动词
(1)can/could
①表示能力
However great the difficulties may be, we can overcome them.
哪怕是再大的困难我们也能克服。
②表示请求与许可
Could/Can I borrow your reference books
我可以借用你的参考书吗？
③表示可能性(常指理论上或习惯上的可能性)
Peter can be really difficult at times even though he is a nice person in general.
总体而言，彼得是一个很好的人，但是有时他也很难相处。
④表示推测(只用于疑问句和否定句中)
—Someone is knocking at the door. Who can it be
——有人在敲门，会是谁呢？
—It can’t be Jim. He is still at school.
——一定不是吉姆，他还在上课呢。
(2)may/might
①表示许可或征询对方的许可
You may take whatever you like.
你喜欢什么就拿什么。
②表示可能性，有“或许、可能”的意思，多用于肯定句中，语气较弱。
They might be having a meeting, but I’m not sure.
他们有可能正在开会，不过我不肯定。
③表示祝愿，用于祈使句中；常用“May＋主语＋动词原形”。
May you succeed！ 祝你成功！
④对含有may的一般疑问句的否定回答形式是：No, you mustn’t./No, you may not./No, you can’t./No, you’d better not.
⑤may/might as well这种结构表示有礼貌的劝告，常译为“还是……为好”。
There is nothing to do, so I may as well go to bed.
没什么事情可做，我还是上床睡觉好了。
(3)must
①表示“必须，应该”
We must do everything step by step.
我们必须逐步做每件事。
②表示推测，意为“一定，必定”，只用于肯定句中，语气较强。
He must be ill. He looks so pale.
他一定是病了。他的脸色很苍白。
③表示“非要，偏偏”
If you must smoke, do it outside, please.
如果你一定要吸烟，请到外面去吸。
④mustn’t表示“禁止”
Smoking mustn’t be allowed in the office.
办公室里不许吸烟。
⑤对含有must的一般疑问句的否定回答形式是：No, you needn’t./No, you don’t have to.
—Must we hand in our exercise books now
——我们现在必须要交练习本吗？
—No, you needn’t./No, you don’t have to.
——不，你们不必。
(4)shall
①用于第一、第三人称疑问句， 表示征询对方意见或请求指示。
Shall I open the window
我能打开窗户吗？
②用于第二、第三人称陈述句，表示命令、允诺、警告、威胁、决心等。
You shall have my answer tomorrow.
你明天可以得到我的答复。
③用于法律、协定、条约等文件中。
The interest shall be divided into five parts, according to the agreement made by both sides. 根据双方的协定，利息应分为五部分。
(5)should/ought to
①意为“应该，应当”(表义务、责任)。
You should/ought to be polite to your teachers. 你应该对老师有礼貌。
②意为“按理说，按理应该”(表逻辑推测)。
She promised to come by 10 o’clock. She should/ought to be here at any moment.
她答应10点之前来，她随时都可能来到这儿。
③should还可表示“竟然”(含惊讶意味)。
It’s surprising that Mary should love such a person as Jack.
玛丽竟然爱上像杰克这样的人，真是让人惊讶。
(6)will/would
①表示意志、意愿、决心等
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表示请求、建议等
Will you close the window It’s a bit cold.
请你把窗户关上好吗？有点冷。
③表示规律性或倾向性
The door wouldn’t open, no matter how hard Granny pushed.
无论奶奶怎么使劲推门，门都不开。
Fish will die out of water.
鱼离开水就会死。
④would常指过去的习惯、习性或倾向等。
Every time she was in trouble, she would go to him for help.
她每次遇到麻烦都会向他求助。
(7)dare/need
①need表示“需要”；needn’t表示“不必”。
—Need he come now
——他现在需要来吗？
—Yes, he must./No, he needn’t./No, he doesn’t have to.
——是的，他必须来。/不，他不必来。/不，他不必来。
②dare既可用作情态动词，又可用作实义动词。用作情态动词时，主要用于疑问句、否定句和条件从句中，一般不用于肯定句中。
The girl didn’t dare (to) go home.
这个女孩不敢回家。
Do you dare to jump into the ocean
你敢跳进海里吗？
They daren’t ask for any more money.
他们不敢再要钱了。
2.“情态动词＋have done” 的6种用法
Sorry，I’m late. I might have turned off the alarm clock and gone back to sleep again.
对不起，我迟到了。我可能把闹钟关掉后又睡着了。
Look! There are so many mistakes in your composition. You should have fixed full attention on it.
看！你的作文里有这么多的错误。你本应该把所有的注意力都集中在它上面的。
1.can与be able to
表示“经过努力设法做成某事”时不用can，应用be able to。can表示“能力”时，侧重于因有某种知识和技能而能办到某事。
【典例】 用could或was able to填空
The fire spread through the hotel very quickly，but everyone____________ get out.
疑难突破
解析 由句意可知，此处应该是所有人经过努力最后出去了，所以应该用was able to。
答案 was able to
2.can’t与may not表示推测
can’t表示“不可能”，may not表示“可能不，或许不”。很明显，can’t比may not语气强。
【典例】 It ________ be the postman at the door.It’s only six o’clock now.
答案 can’t
解析 can’t不可能，在此表示有把握的否定推测，符合句意。
3.can’t，mustn’t，needn’t
can’t指“无能力”；mustn’t指“不允许，一定不要”；needn’t指“不必”。
【典例】 用can’t，mustn’t或needn’t填空
①There is a meeting inside.You__________ make any noise.
答案 mustn’t
解析 句意：里面在开会，你不许制造任何噪音。故应填mustn’t。
②He is so young that he ___________ make a living.
解析 句意：他太小了不能维持生计。故应填can’t。
答案 can’t
③According to today’s weather report，it does not rain，so you___________ take the umbrella.
解析 句意：根据今天的天气预报，今天不下雨，所以你没有必要带雨伞。故应填needn’t。
答案 needn’t
1.You ____________ be Carol.You haven’t changed a bit after all these years.
2.Life is unpredictable; even the poorest ____________ become the richest.
3.I still remember my happy childhood when my mother ____________ take me to Disneyland at weekends.
即时训练
选词填空(would，shall，must，might, can，should)
must
might
would
4.—Can I pay the bill by check
—Sorry, Sir.But it is the management rules of our hotel that payment ____________ be made in cash.
5.The giant panda looks very mild.But it ____________ be very fierce when you annoy it.
6.The players from Shanghai Football Club have been doing very well recently, so they ____________ win the final match.
shall
can
should
1.虚拟语气用于条件句中的4种情况
考点2 虚拟语气
If there were no air，we couldn’t live.
如果没有空气，我们就不能生活。
If there had been no air in the tube，the result of the experiment would have been more accurate.
如果管子里没有空气，实验的结果就会更精确。
If he were to come tomorrow, things would be easier.
如果他明天来，事情就容易多了。
2.虚拟语气用于名词性从句中的4种条件
(1)在“It is＋important/necessary/natural/strange/essential/vital/a pity＋that ...”句型中，谓语动词用“(should＋)动词原形”。
It’s vital that we (should) take our safety driving along the road seriously.
重视道路安全驾驶是至关重要的。
(2)在would rather (that)后的宾语从句中，从句的谓语动词如果表示现在或将来要发生的动作，从句用一般过去时；如果表示过去发生的动作，从句用过去完成时。
I’d rather he had gone to the seaside with me the day before yesterday.
要是他前天和我去海边就好了。
(3)句中含有以下单词或其变形时，该句中的名词性从句(宾语从句、表语从句、主语从句、同位语从句)部分常用虚拟语气，其谓语动词形式为“should＋动词原形”，其中should可以省略。
He suggested that we (should) start off early the next day.
他建议我们第二天早点出发。
(4)wish后宾语从句中的虚拟语气
①对现在的虚拟： 过去式(be的过去式用were)
②对过去的虚拟： had＋过去分词
③对将来的虚拟：would/could/might＋动词原形
I wish (that) I were ten years younger.
我希望我能年轻十岁。
I wish (that) I had met that film star yesterday.
我希望我昨天见到了那位电影明星。
3.3个特定句式中的虚拟语气
If only I had seen the film.
要是我看过那部电影就好了。
It is high time that we started/should start out.
我们该出发了。
He messed the project up, but he behaved as if nothing had happened.
他把计划搞砸了，但他表现得若无其事。
1.虚拟条件句中的省略与倒装
如果虚拟条件句中含有were/had/should，有时可把if省略，把were/had/should提到主语之前形成倒装；若为否定形式，not不可提前。
Had he caught the morning train, he would not have been late for the meeting. 要是他赶上了早晨的火车，那他开会就不会迟到了。
疑难突破
2.错综时间条件句
有时条件句的动作与主句动作发生的时间不一致，这时动词的形式应根据它们各自发生的时间加以调整。
If we had booked a table earlier, we wouldn’t be standing here in a queue. (if条件句是对过去的虚拟，而主句是对现在的虚拟)
如果我们早些订位子，现在也就不用站在这里排队了。
3.含蓄虚拟条件句
(1)有时假设的情况不用条件句表达，而是用but for, without等介词(短语)来表示。
We wouldn’t have finished the project on time without your timely help.
如果没有你的及时帮助，我们就不能按时完成那项工程。
(2)用连词otherwise, or等暗示后文与前面的情况相反，从而引出后文的虚拟语气。
(3)虚拟条件通过but暗示出来，模式为“虚拟情况＋but＋真实情况”。
1.But for your help we ____________________________________________.
如果没有你的帮助，我们的实验是不会成功的。
2.If a person’s clothes were dirty and worn, he __________________________，
and annoy him in every way.
如果遇见衣衫褴褛的人，他就会拿石头砸过去，或者用其他手段骚扰人家。
即时训练
补全句子
couldn’t have succeeded in the experiment
would throw stones at him
3.If you had come a few minutes earlier，you ____________________________
___________the famous singer.
如果你早来几分钟，你就会见到那个著名歌手了。
4.It’s high time that we ______________________________________________
____________.
是我们致力于环境保护的时候了。
5.They talked and talked as if/though they ____________________________.
他们说个不停，好像永远不会再见面一样。
would(should/could/might)
have met
should devote/devoted ourselves to environmental
protection
would never meet again
层级一 模拟达标练
单句语法填空/单句改错
分层演练
1.(2022·合肥模拟)The new airport complex，consisting of a main terminal, a supporting service building and a parking lot, ____________ (cover) an area of about 1.4 million square meters.
2.(2022·衡水五调)Known as the “Sea Garden”，Macao, while filled with luxury and world－class entertainment，also ____________ (offer) many landmarks that define the city’s unique and fascinating culture.
covers
offers
3.(2022·南京十校5月调研)He had his eyes on me, and I guessed he _______________(consider) right then whether or not to tell me the truth.
4.(2022·河南省实验期中)Since scientists in Scotland successfully cloned a sheep and named the newborn Dolly, the clone technology ________________________________ (advance) slowly but steadily.
5.(2022·湖北黄冈八模)US writer Margaret Lee Runbeck once _____________ (write) “Happiness is not a station you arrive at, but a manner of traveling.”But traveling is not always happy, at least for the buddies in the movie Green Book. The movie ____________ (adapt) from the true story of a road trip through the southern US in the early 1960s.
was considering
has advanced/has been advancing
wrote
was adapted
6.(2022·南京十校5月调研)By the time the ban was finally lifted, he ________________ (stick) at the airport for more than two weeks.
7.(2022·北京西城区统一测试)5G is the innovation that ______________(shape)all our lives for years to come.
8.(2022·宁波十校联考)Since 1972, more than 800 cultural sites that are thought to be of special importance to human history and culture _________________ (add) to the World Heritage List.
9.My computer didn’t start this morning. There ____________ have been something wrong with it.
had been stuck
will shape
have been added
must
10.The number of the children who own the iPads ____________ (be) growing all the time.
11.(2022·衡水中学一模)Hurry up, kids! The school bus was waiting for us！____________
12.(2022·江西九江高三一模)When I first meet Bryan I didn’t like him, but I have changed my mind.____________
13.(2022·福州质检)She was phoning someone, so I nod to her and went away.______________
14.(2022·陕西渭南一模)I am sorry I didn’t go to the cinema with you yesterday. You know, I have seen the film.____________
is
was→is
meet→met
nod→nodded
have→had
Ⅰ.单句语法填空
1.(2021·新高考卷Ⅰ)You can’t help wondering how hard it ____________ (be) for the people then to put all those rocks into place.
2.(2021·全国甲卷)The Xi’an City Wall is the most complete city wall that has survived China’s long history. It ____________ (build) originally to protect the city in the Tang dynasty and has now been completely restored (修复).
3.(2021·全国甲卷)We ____________ (hire) our bikes from the rental place at the South Gate. My bike was old and shaky but did the job.
层级二 高考真题练
was
was built
hired
4.(2021·浙江卷)It doesn’t impress like George Washington’s plantation on the Potomac, but Lincoln’s home in downtown Springfield, Illinois, ________________________(prove)irresistible to visitors since it opened to the public.
5.(2020·全国卷Ⅰ)The unmanned Chang’e－4 probe (探测器)—the name was inspired by an ancient Chinese moon goddess—____________ (touch) down last week in the South Pole－Aitken basin.
6.(2020·全国卷Ⅱ)Chinese New Year is a celebration marking the end of the winter season and the beginning of spring.This is why decorating with plants，fruits and flowers ____________ (carry) special significance.
has proved/has proven
touched
carries
7.(2020·全国卷Ⅱ)Actually，I ____________ (start) to learn kung fu when I was seven years old，but I have long been out of practice.
8.(2020·全国卷Ⅲ)For example, every morning, my dad has to have a bowl of egg soup while I ____________ (have) to eat an apple.My dad doesn’t like the soup and I don’t enjoy apples.
9.(2020·新高考卷Ⅰ)The parts of a museum open to the public ____________(call) galleries or rooms.Often, only a small part of a museum’s collection is on display.
started
have
are called
10.(2019·全国卷Ⅱ)Picking up her “Lifetime Achievement” award, proud Irene ____________(declare) she had no plans to retire from her 36－year－old business.
declared
Ⅱ.单句改错
1.(2021·全国乙卷)I also water the flowers in the yard and tidying up my own bedroom whenever necessary._________________
2.(2021·全国甲卷)One of the questions are: Who will you go to in times of trouble？_________________
3.(2020·全国卷Ⅱ)Actually, I start to learn kung fu when I was seven years old, but/yet I have long been out of practice._________________
4.(2019·全国卷Ⅲ)Now my dream is to open a cafe.Though it may appear simple, it required a lot of ideas and efforts.___________________
tidying→tidy
are→is
start→started
required→requires
5.(全国卷Ⅱ)I didn’t realize how right my parents are until I entered high school. __________________
6.(全国卷Ⅲ)It was Monday morning, and the writing class had just begin.__________________
7. (全国卷Ⅲ)About one month after this photo was taken, I entered my second year of high school and become a new member of the school music club.__________________
8. (全国卷Ⅲ)However, my parents didn’t seem to think so. They always tell me what to do and how to do it.____________
are→were
begin→begun
become→became
tell→told
9. (全国卷Ⅰ)Since then—for all these years—we had been allowing tomatoes to self－seed where they please.____________
10. (全国卷Ⅰ)Lots of studies have been shown that global warming has already become a very serious problem. ____________
had→have
去掉been
Ⅰ.语法填空
The first zoo 1._________________(establish) around 3，500 years ago by an Egyptian queen for her personal enjoyment.Five hundred years later，a Chinese emperor 2.____________ (build) a huge zoo to show his power and wealth.Later zoos were set up for the purpose of studying animals.
层级三 语篇提能练
Some of the early European zoos 3.____________ (consist) of dark holes or dirty cages，the bad conditions of which made people disgusted.Later the zoos 4._______________ (replace) by research centers and animals there were studied and 5._______________ (keep) in good condition.These places became the first modern zoos.As early as the 1940s，scientists 6.____________ (understand) that many kinds of wild animals faced extinction.Since then，zoos 7.________________ (try) to save many endangered species，but relying on zoos 8.________________ (save) species is not enough.The best method of protection is to leave them in their natural habitat.
Today，animals in large and natural reserves are fed a balanced diet and 9.______________ (watch) carefully for any signs of disease with specially trained keepers looking after them and some hospitals where they can be treated when ill，and all the animals there live a comfortable life.Anyway，it is true that zoo breeding programs 10.______________ (play) an important role in protecting many species of wildlife now.
答案
1.was established [考查时态语态和主谓一致。根据时间状语“around 3，500 years ago”可知是过去时态，主语“The first zoo”和谓语动词establish 是被动关系。又因主语是第三人称单数，故填 was established。]
2．built [考查时态。句中“Five hundred years later”是过去的时间状语，谓语需要用过去式，故填 built。]
3．consisted [考查时态。本句的语境是过去，谓语动词用过去式，故填 consisted。]
4．were replaced [考查时态语态和主谓一致。主语“the zoos”和谓语动词replace 为被动关系，并且是过去时态，且主语是复数，所以用were replaced。]
5．(were) kept [考查时态语态和主谓一致。“animals there were studied and________”为并列关系，故填(were) kept。]
6．understood [考查时态。“As early as the 1940s”是过去的时间状语，谓语要用过去式，故填 understood。]
7．have tried/have been trying [考查时态和主谓一致。时间状语为“Since then”，谓语常用现在完成时，此处也可用现在完成进行时表示动作一直持续进行。又因主语zoos是复数，故填have tried/have been trying。]
8．to save [考查非谓语动词。rely on sb to do sth 依靠某人做某事，故填to save。]
9．(are) watched [考查时态语态和主谓一致。主语animals和谓语动词watch 是被动关系，且此处与and前面的are fed...为并列关系，故填(are) watched。]
10．are playing [考查时态和主谓一致。由时间状语now可知，此处应该使用现在进行时。故填 are playing。]
Ⅱ.短文改错
The date of my departure for Wellington is drawing nearly，and I am busy with preparations.I have been signed up for a one－month advanced course arranging for high school students.Studying there is expensive but I think it would be meaningful.To help to cover the cost of my study，I decide to find the part－time job there.It’ll be great if I succeed finding one before I arrive.Fortunately，my aunt Sally，who has a wide social network in Wellington than me，can lend me a hand. She told me there might be anyone in need of a house cleaner，gardener，and babysitter for their children.I’m really looking forward to my study tours in Wellington.
答案与解析
①副词误用。nearly作副词意为“几乎，差不多”，near作副词意为“临近”。根据句意可知，此处应用near。
②语态误用。sign up for“报名参加”与主语I是主动关系，故应用现在完成时的主动形式。
③非谓语动词误用。分析句子结构和句意可知，此处非谓语动词作后置定语修饰course，arrange与course是逻辑上的动宾关系，故用动词的－ed形式作定语。
④时态误用。此处表达从现在看将来要发生的事情，故用一般将来时。
⑤冠词误用。此处意为“一份兼职工作”，表示泛指，故用a。
⑥介词漏用。succeed in doing sth“成功做成某事”是固定搭配，in不可以省略。
⑦比较等级误用。根据语境可知，此处有比较的含义，应用形容词的比较级。
⑧代词误用。此处表示她告诉我可能有人需要人来做某项工作，而不是她告诉我会有任何一个人需要，故用someone。
⑨连词误用。根据句意可知，此处表示选择关系，故用or。
⑩名词单复数误用。此处表示作者这次的惠灵顿学习之旅，应该用单数。(共27张PPT)
情态助动词
复
习
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2023.01.19
01
情态助动词
英语动词分成主动词（Main Verb）和助动词（Auxiliary）两大类，情态助动词（Modal Auxiliary）属于助动词，本身具有一定的词义，但必须和动词原形连用构成句子的谓语。它们没有非限定形式和词形变化，大多一词多义，因此在意义和用法上有不少交叉的地方。
情态助动词简介
情态动词的基本用法
1．can和could的用法
(1)表示“能力”。（can表示现在的能力，could表示过去的能力）
—No one can be compared with Yao Ming in playing basketball.
—在打篮球方面，无人能与姚明相媲美。
(2)表示礼貌地请求别人做某事或允许别人做某事，意为“能，可以”。（Permission）
—What should I wear to the party
—Well，it isn't very formal. You can wear whatever you like.
——晚会我应该穿什么？
——晚会不太正式，你可以穿自己喜欢的任何衣服。
（注意：回答时通常用can,不用could）
For instance:
Can/Could I use you dictionary
-Yes, you can.
情态动词的基本用法
1．can和could的用法
(3)表示惊讶，常用在否定句和疑问句中。
How could you do such a silly thing
你怎么能做那样的蠢事呢？
can’t表示 “不可能”，用于表示把握比较大的推测
注：the differences between “can” and “be able to”
表“能力”可互换
Can 只有原形和过去式；be able to 可有各种时态
用在过去时中，could do 表示过去的一般能力，而was/were able to 表示做某件具体事情的“能力”
情态动词的基本用法
2．may和might的用法
(1)may和might表示“许可”。（Permission）
—May I take the book out
—I'm afraid not.
——我能将书带出去吗？
——恐怕不行。
might 表示请求时语气更委婉。
might表示请求时，对其进行肯定回答用may/can，而不用might
(2) 表示推测，意为“可能，或许”，通常不用于疑问句中。
She may be at home today.
(3) may用于祈使句中表示祝愿
May you be happy forever!
may well和may as well结构
(1)“may well＋动词原形”是一种常用结构，意为“完全能，很可能”，相当于“be very likely to do”。如：
He may well be proud of his son.
他大可为他的儿子感到自豪。
(2)“may as well＋动词原形”意为“最好，倒不如”。如：
You may as well do it at once.你最好马上就做这件事。
We may as well stay where we are.我们留在现在的地方倒也不错。
情态动词的基本用法
3．must的用法
(1)表示必要性，意为“必须”。
The children must be back by 4 o'clock.
孩子们必须4点钟以前回来。
(2)表示禁止(用于否定句)。
You mustn't park here！It's an emergency exit.
你不可以在这儿停车！这是紧急情况出口处。
(3) 表示推测，语气最为肯定，一般用于肯定句，意为“一定，准是”
She must be tired after such a long walk.
情态动词的基本用法
4．shall和should的用法
(1)shall的用法
①用于第一、第三人称疑问句中，表示说话人征求对方的意见或向对方请示。
Shall I go out for a walk after supper
晚饭后我可以散散步吗？
②shall与第二、三人称连用，用于陈述句中，表示说话者的意志，用来表达说话者给对方以命令、指示或允诺。此外，当宣布法律、规定时，也用shall来表达。如：
—Will you read me a story，Mummy
—OK. You shall have one if you go to bed as soon as possible.(允诺)
It has been announced that candidates shall remain in their seats until all the papers have been collected.
已宣布，在所有试卷收上来之前，应试者必须留在自己的座位上。(规则或规定)
情态动词的基本用法
4．shall和should的用法
(2)should的用法
should意为“(义务上)应该”，在语气上比must(必须)弱。“should＋动词原形”表示现在或将来应该……。如：
I should go and visit him this afternoon，but I wonder if I will be free.
今天下午我应该去看望他，但我不知道我是否有空。(表示将来应该)
The children should be taken good care of.
这些孩子应该受到好的照顾。
表示惊讶、忧虑、惋惜等情绪，意为"竟会,竟然"。
It’s a pity that you should be so careless. Why should anyone want to marry Tony
情态动词的基本用法
5．will和would的用法
(1)表示意志、意愿和决心，would用于过去的情况。
You can stay here as long as you can，if you will.
如果你愿意，你能在这里待多长时间就待多长时间。(表示主语的意愿)
(2)will(won't)可用来叙述真理，还可叙述目前的习惯，would(wouldn't)可以用来叙述过去的习惯。如：
Oil will float on water.油能浮在水面上。
She will listen to records alone in her room for hours.
她独自一人在屋里听唱片，常常一听就是几个小时。
He would spend hours in the bathroom or on the telephone.
他以前一进洗澡间或是一打电话，往往就是几个小时。
情态动词的基本用法
5．will和would的用法
特别注意：would和used to都可表示过去的习惯，但前者表示过去反复的动作，常与every day，often，frequently等连用；后者表示过去的状态或过去的习惯，但现在已不存在。如：
When he was abroad，he would read as many books as possible.在国外时，他总是尽可能多读书。
She doesn't get up so early as she used to.她不像以前那样起得那么早了。
情态动词的基本用法
6．need和dare的用法
need和dare两者既可用作情态动词也可用作实义动词。作实义动词时，有人称和数的变化，可用于肯定句、否定句或疑问句中，构成否定句或疑问句时要用助动词do，does，did；作情态动词时，没有人称和数的变化，直接接动词原形，只用于否定句和疑问句中，构成否定句和疑问句时不用助动词。
另外，dare作情态动词时，还可用于条件句中，过去式为dared；作实义动词时，dare常用于疑问句或否定句，后面的to也可省略；I dare say是习惯说法，意为“我想，大概”。
情态动词的基本用法
6．need和dare的用法
He needn't do it.(情态动词)
He doesn't need to do it.(实义动词)
他不必做这件事。
I didn't know whether he dared say that to him.(情态动词，有时态变化)
我不知道他是否敢对他说那话。
He didn't dare(to) do it.(实义动词)
He dared not do it.(情态动词)
dare的习惯用法:
1. I dare say. 也许，我想
e.g. It will rain this afternoon, I dare say.
2. How dare+句子。"……竟敢……
表示对他人行为感到愤怒
e.g. How dare you open my drawer without my permission!
情态动词基本语法功能:
用法 请求/许可 可能/推测 义务/职责 意图/打算 意愿/愿意 意志/决心 才能/能力
can/could √ √ √
may/might √ √
shall/should √ √ √ √ √ √
will/would √ √ √ √ √
must √ √
ought to √ √
02
“情态动词+ have done”结构
“情态动词+have done”既可表示对过去情况的推测,又可表示某种情绪、态度。情态动词不同，该结构所表示的含义也不同。
1．should/ought to＋have done
表示“过去本应该做而(实际)没有做的事情”，含有责备或遗憾的语气，意为“本应该……”。其否定形式为“should not/ought not to＋have done”，表示某种行为本不该发生但实际上发生了。
You ought to have done this exercise more carefully.
你本应该更仔细地做这个练习。
You shouldn't have told her the truth.
你本不该告诉她真相。
2．must＋have done
用于肯定句，表示“过去一定做过某事”，是一种很有把握的推测。注意：对过去发生的情况的否定推测常用“can't/couldn't＋have done”表示。
—Ye Shiwen won two gold medals in London Olympic Games.
—She must have gone through tough training.
——叶诗文在伦敦奥运会上获得了两枚金牌。
——她肯定受过严格的训练。
It must have rained last night, for the road is quite muddy.
昨晚一定下雨了，因为路很泥泞。
3．may/might＋have done
是对过去情况的一种不太有把握的推测，表示“可能已做了某事……”，否定句表示“可能还没有……”。
Sorry, I'm late. I might have turned off the alarm clock and gone back to sleep again.
对不起，我迟到了。我可能把闹钟关掉后又睡着了。
4．could＋have done
表示“过去本来可以做，但实际上没有做”；can/could＋have done表示“过去可能做过”。
I could have saved the poor rabbit, but I didn't have the right drugs with me at that moment.
我本来可以拯救那只可怜的兔子的，可是我当时没有合适的药品。
5．needn't＋have done
表示“过去没有必要做某事，但实际上做了某事”。
Mark needn't have hurried.After driving at top speed，he arrived half an hour early.
马克本没必要那么匆忙。他以最快速度开车，结果早到了半个小时。
You needn't have taken a taxi here，for it was very near to my house.
你本来不必打车来这里的，因为这里离我家很近。
03
实操练习
1. I can’t find my purse. I ________ it in the supermarket yesterday, but I’m not sure. (2018年天津卷单项填空)
A. should leave B. must have left
C. might leave D. could have left
D
2. In today’s information age, the loss of data _________ cause serious problems for a company. (2018年北京卷单项填空)
A. need B. should
C. can D. must
C
I. 选用括号内合适的内容补全下面句子。
1. I'm sorry I couldn't get in touch with him before he left. I __________________ (should have phoned, have phoned) him earlier.
2. Since they aren't answering their telephone, they ______________ (can have left, must have left).
3. You ____________ (will, may) lead a horse to the water but you _________ (dare, can) not make it drink.
should have phoned
must have left
may
can
4. Mary _____________________ (couldn't have received, needn't have received) my email; otherwise she would have replied before now.
5. You ____________ (mustn't, needn't) do that if you don't want to.
6. I don't believe him. He ________ (may not, can't) be serious.
7. If you don't like to swim, you _______________ (may as well, may well) stay at home.
couldn't have received
needn't
can't
may as well
8. They hurried there only to find the meeting canceled. In fact, they __________________ (needn't have gone, wouldn't have gone) at all.
9. She was ill. She ______________________ (couldn't have attended, mustn't attend) the meeting here.
10. Carey didn't go to the party last night because she ________________ (should look after, had to look after) the baby for her sister until 9:30.
needn't have gone
couldn't have attended
had to look after
