【单元考点培优】Unit 7 专题07 句型转换-2025-2026学年九年级全册英语单元复习考点培优（含答案解析）

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2025-2026学年九年级全册英语单元复习考点培优人教新目标Unit 7 Teenagers should be allowed to choose their own clothes
专题07 句型转换
学校:___________姓名：___________班级：___________考号：___________
1．We should carry out the plan. (变为被动语态)
2．I must do all the exercise in time. (变成被动语态)
3．We must keep this in mind. (变为被动语态)
4．The children may sing an English song. (被动语态)
An English song by the children.
5．You can find a lot of differences between the two languages. (被动语态)
A lot of differences between the two languages by you.
6．The television must be repaired. (改为一般疑问句，并作否定回答)
— the television
—No, it .
7．Someone might use smartphones to take pictures instead of cameras. (改为被动语态)
Smartphones to take pictures instead of cameras.
8．People can take off the heavy coats in early spring.（改为被动语态）
The heavy coats by people in early spring.
9．The lights should be turned off when you leave the classroom. (改为主动语态)
You the lights when you leave the classroom.
10．The flowers shouldn’t be picked by us. They have life, too. (改为主动语态)
We . They have life, too.
11．You can't lend the book to others.(改为被动语态)
The book to others.
12．The young trees should be watered every day. (改为否定句)
The young trees every day.
13．You must look after her well.(改为被动语态)
She must well by you.
14．This project can be finished in three months.(改为一般疑问句)
this project in three months
15．We should brush our teeth twice a day. (改为被动语态)
Our teeth should twice a day.
16．I think we can leave for home now. (改为否定句)
I we can leave for home now.
17．We can train some kinds of dogs to guide blind people. (改为被动语态)
Some kinds of dogs can to guide blind people.
18．The weather was so awful yesterday. (改为感叹句)
weather it was yesterday!
19．They can solve the problems of the motor vehicles this month. (改为被动语态)
The problems of the motor vehicles can this month.
20．We should encourage teenagers to read more books. (改为被动句)
Teenagers should to read more books.
21．People mustn’t park private cars in this street. (句子改为被动语态，每空一词。)
Private cars by people in this street.
22．Parents must stop children from playing computer games too much. (句子改为被动语态，每空一词。)
Children playing computer games too much by parents.
23．They may send these sports goods to schools in mountains. (句子改为被动语态，每空一词。)
These sports goods to schools in mountains by them.
24．Teachers should allow students to speak out their own thoughts. (句子改为被动语态，每空一词。)
Students speak out their own thoughts by teachers.
25．I think the students should be allowed to go out with their friends.（改为一般疑问句）
the students should be allowed to go out with their friends
26．The boy should be allowed to play on Sundays.（改为否定句）
The boy allowed to play on Sundays.
27．I planted the young tree this spring.(改为被动句)
28．You can take the book home.（改为被动句）
The book home.
29．We gave him lots of gifts last Friday. (变为被动语态)
Lots of gifts him last Friday.
30．The dog should be fed every day. (改为一般疑问句)
the dog every day
31．Students should finish their homework on time.（改为被动语态）
Their homework be by students on time.
32．Lots of Chinese speak English now. (变为被动语态)
English by lots of Chinese now.
33．Parents should give their children more chances to be with family. (变为被动语态)
Children should more chances to be with family by parents.
34．We must send the sick man to the hospital.（将主动语态的句子改成被动语态）
35．We should teach these children to swim. (将主动语态的句子改成被动语态)
36．We can see no stars in the daytime. （变为被动语态）
No stars can in the daytime.
37．People needn’t show the travel code（行程码）any longer. （改为被动语态）
The travel code needn’t any longer.
38．We can see paper cutting in many parts of China during the Spring Festival.(改为被动语态)
Paper cutting can in many parts of China during the Spring Festival.
39．When we draw a cartoon face, we should make some parts of the face bigger to make it look funnier. (改为被动语态)
When we draw a cartoon face, some parts of the face should bigger to make it look funnier.
40．Our teacher should allow us to play football for one hour every day. (改为被动语态）
We should to play football for one hour every day.
41．We should clean the classroom every day.（改为被动语态）
The classroom should every day.
42．They should pay attention to their handwriting if they want to get a higher score. (改为被动句)
Their handwriting should attention to if they want to get a higher score.
43．The students should sweep the floor every day. (改为被动语态）
The floor should by the students every day.
44．The government should do something to make the city clean. (改为被动语态)
Something should by the government to make the city clean.
45．We must obey the school rules and traffic rules. (改为被动语态)
The school rules and traffic rules must by us.
46．We must clean our classroom every day.(改为被动语态)
Our classroom must every day by us.
47．You needn’t write the letter right now. （改成被动）
The letter be right now.
48．Students can’t take magazines out of the reading room without permission.(改为被动语态)
Magazines out of the reading room without permission by students..
49．We should encourage school children to spend some time on team sports.(改为被动语态)
School children should to spend some time on team sports.
50．We can write the rules out and put them up the walls.（改为被动句）
The rules can out and put up on the walls.
51．You should write all the answers on the answer sheet. （改成被动语态）
All the answers should on the answer sheet.
52．Teenagers should be allowed to choose their own clothes. (改为一般疑问句)
teenagers allowed to choose their own clothes
53．All schools must offer delay service according to the new policy.（改为被动语态）
Delay service must by all schools according to the new policy.
54．We must take good care of the old people in our country.（改为被动语态）
The old people must good care of in our country.
55．Children under 12 years old should be allowed to leave at home alone.（改为否定句）
56．Students should be allowed to do homework with friends.（改为否定句）
.
57．You must not plant trees in the dry soil.（改为被动语态）
Trees in the dry soil.
58．We must keep food in the refrigerator so that it doesn’t go bad easily. (改为被动语态)
Food must in the refrigerator so that it doesn’t go bad easily.
59．Students should make plans for their summer holidays. (改为被动语态)
Plans should for students’ summer holidays.
60．We can share many things, such as bikes, cars and umbrellas.（改为被动语态）
Many things can , such as bikes, cars and umbrellas.
61．We should teach our students some necessary living skills. (改为被动语态)
Our students should some necessary living skills.
62．Nobody can answer the question. (改为被动语态)
The question answered by anybody.
63．We will hold a class meeting to talk about teamwork next Friday.（改为被动语态）
A class meeting will to talk about teamwork next Friday.
64．We must keep our classroom clean and tidy every day. (改为被动语态)
Our classroom must clean and tidy every day.
65．We must keep the noise under 50 dbs (分贝).（改成被动句）
The noise must under 50 dbs.
66．We can’t see many of the stars. （改为被动语态）
67．They can organize an English speech contest in two weeks.（改为被动语态）
An English speech contest can by them in two weeks.
68．You must finish the work on time. (改为被动语态)
The work must on time.
69．You needn’t do it now. (改为被动语态)
It by you now.
70．Teachers should encourage students to speak out their own thoughts.（改成含被动语态的句子）
Students speak out their thoughts by teachers.
71．Parents must stop children from playing computer games too much. （改成含被动语态的句子）
Children playing computer games too much by parents.
72．Shops can’t sell cigarettes to teenagers. （改成含被动语态的句子）
Cigarettes to teenagers by shops.
73．He should be told about the meeting.（改为一般疑问句）
he told about the meeting
74．You must give back the dictionary before Friday. (改为被动语态)
The dictionary must back before Friday.
75．You must return the book on time. (改为被动语态的一般疑问句形式)
the book on time
76．We must put used batteries into these green bins.（改为被动语态）
Used batteries must into these green bins.
77．You should make up the bed every day. （改为被动语态）
The bed up every day.
78．We can’t see stars in the day time. (改为被动语态)
Stars in the day time.
79．Tom should write an answer letter to his boss.(改为被动语态)
An answer letter should to his boss by Tom.
80．We must keep the noise under 50dbs(分贝）here.(改为被动语态）
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参考答案及试题解析
1．The plan should be carried out./The plan should be carried out by us.
【解析】句意：我们应该执行这个计划。含有情态动词的被动语态结构为“情态动词+be+过去分词”；原句中的宾语“the plan”变为主语；原句中的谓语“should carry out”变为“should be carried out”；原句中的主语“We”在被动语态中用by引出，放在句末，如果不需要强调动作的执行者，by部分可以省略。故填The plan should be carried out (by us).
2．All the exercise must be done in time.
【解析】句意：我必须及时做所有练习。将主动语态变为被动语态时，需将宾语all the exercise变为主语；原句有情态动词must，被动结构为“must be+过去分词”，do的过去分词是done，故填All the exercise must be done in time.
3．This must be kept in mind./This must be kept in mind by us.
【解析】句意：我们必须记住这一点。含有情态动词的被动语态结构为“情态动词+be+过去分词”；原句的宾语“this”作被动语态的主语；原句的谓语“must keep”变为被动形式“must be kept”；原句的主语“We”在被动语态中由by引出放在句末，改为us，如果不需要强调动作的执行者，by部分可省略。故填This must be kept in mind (by us).
4．may be sung
【解析】句意：孩子们可以唱一首英文歌。原句含有情态动词may，含有情态动词的被动语态的结构是：情态动词+be+动词过去分词，原句动词sing的过去分词是sung。故填may；be；sung。
5．can be found
【解析】句意：你可以发现这两种语言之间有很多不同之处。原句中含有情态动词can，含有情态动词的被动语态的结构是：情态动词+be+动词过去分词，原句动词find的过去分词是found。故填can；be；found。
6．Must be repaired needn’t
【解析】句意：这台电视机必须修理。根据英语句子与汉语要求可知，原句为含有情态动词“must”的句子，因此改为一般疑问句时，需要把情态动词提至句首，首字母大写，其他句子成分照抄；must提问的句子否定回答用“No, 主语+needn’t”。故填Must；be；repaired；needn’t。
7．might be used
【解析】句意：有些人可能会用智能手机而不是相机拍照。根据所给英文句子以及汉语要求可知，原句为含有情态动词“might”的句子，其被动语态构成为：情态动词+be+动词的过去分词。故填might；be；used。
8．can be taken off
【解析】句意：人们可以在早春脱下厚重的外套。考查主动语态变被动语态。原句是一般现在时，应改为一般现在时的被动语态，情态动词can后为动词原形，结构为can be done。take的过去分词是taken。故填can；be；taken；off。
9．should turn off
【解析】句意：当你离开教室时，这些灯应该被关掉。原句为含情态动词should的被动语态，其结构为should be done；改成主动语态时，其结构为should do，意思“应该允许”，过去分词turned的动词原形为turn。故填should；turn；off。
10．shouldn’t pick flowers
【解析】句意：这些花不应该被我们摘掉。它们也有生命。原句为含情态动词should的被动语态，其结构为shouldn’t be done；改成主动语态时，其结构为shouldn’t do，意思是“不应该做”，过去分词picked的动词原形为pick。原句的主语变为宾语。故填shouldn’t；pick；flowers。
11．can’t be lent
【解析】句意：你不能把书借给别人。含有情态动词的被动语态结构为：情态动词 + be + 动词的过去分词，lend的过去分词是lent。故填can’t；be；lent。
12．shouldn’t be watered
【解析】句意：应该每天给这些小树浇水。分析题干可知，句子为含情态动词should的被动语态，其结构为should be done；变为否定句时，只需在should后加not，缩写为shouldn’t，后接be done。故填shouldn’t；be；watered。
13．be looked after
【解析】句意：你必须要照顾好她。被动语态的结构是“主语+be+动词的过去分词+其他”，look的过去分词是looked，must是情态动词，后用be动词的原形be。故填be；looked；after。
14．Can be finished
【解析】句意：这个课题三个月后能完成吗？本题考查改为一般疑问句。根据“can be finished”可知，“can”是情态动词，因此改为一般疑问句时，情态动词“can”提到句首，首字母大写；其余内容照抄。故填Can；be；finished。
15．be brushed
【解析】句意：我们应该一天刷两次牙。句子含有情态动词，应该改为含有情态动词的被动语态，其态结构为“should be done”，brush的过去分词是brushed，故填be；brushed。
16．don’t think
【解析】句意：我想我们现在可以回家了。分析题干可知，此句为含宾语从句的主从复合句，且主句是“I think”，改为否定句时，需要把主句改为否定形式，即“否定转移”，而宾语从句则不需要改为否定形式；主句时态为一般现在时，主语为I，谓语动词为think，变否定句时要借助助动词don’t，后接动词原形think。故填don’t；think。
17．be trained
【解析】句意：我们可以训练某些种类的狗给盲人带路。根据句中“can”一词可知，需改成含情态动词can的被动语态，其结构为can+be +动词的过去分词，train“训练”为谓语动词，其过去分词为trained。故填be；trained。
18．What awful
【解析】句意：昨天的天气真糟糕。改为感叹句修饰的中心词weather是不可数名词，用“what+形容词+不可数名词+主谓”的感叹句结构。故填What；awful。
19．be solved
【解析】句意：这个月他们可以解决机动车辆的问题。根据“can”可知，这里是含有情态动词can的被动语态，结构为can be done；solve的过去分词为solved。故填be solved。
20．be encouraged
【解析】句意：我们应该鼓励青少年多读书。原句改为被动语态，结构是should be done，encourage用其过去分词形式。故填be encouraged。
21．mustn’t be parked
【解析】句意：人们不能把私家车停在这条街上。句子应该为含有情态动词must的被动语态，构成为must + be +动词过去分词，此处为否定句，应用mustn’t，park的过去分词为parked。故填mustn’t；be；parked。
22．must be stopped from
【解析】句意：家长们必须阻止孩子们过多地玩电脑游戏。分析题干，应该为含有情态动词must的被动语态，构成为：must be +动词过去分词，stop...from“阻止某人做某事”，这里应用stop的过去分词。故填must；be；stopped；from。
23．may be sent
【解析】句意：他们可能会把这些体育用品送到山区的学校。句子应改为含有情态动词may的被动语态，构成为：may + be +动词过去分词，send的过去分词为sent。故填may；be；sent。
24．should be allowed to
【解析】句意：老师应该允许学生说出自己的想法。句子应改为含有情态动词should的被动语态，构成为：should + be +动词过去分词；allow to do“允许做某事”，此处allow应用过去分词allowed。故填should；be；allowed；to。
25．Do you think
【解析】句意：我认为应该允许学生和他们的朋友出去。主句“I think”是一般现在时，变为一般疑问句，需要把第一人称变为第二人称；助动词应用do，置于句首，首字母要大写。故填Do；you；think。
26．should not be
【解析】句意：这个男孩星期天应该被允许玩。原句有情态动词should，变否定句时在情态动词后加not，情态动词后跟动词原形be。故填should；not；be。
27．The young tree was planted by me this spring
【解析】句意：今年春天我种下了这棵小树。该句时态为一般过去时，一般过去时的被动语态结构为“was/were+动词过去分词”，原句宾语“the young tree”变为被动句的主语，为单数，则be动词用“was”，即“The young tree was planted”，其后用“by+原句主语(代词变为宾格形式)”，即“by me”，后面时间状语“this spring”照着写下来。故填The young tree was planted by me this spring.
28．can be taken
【解析】句意：你可以把书带回家。结合can可知，本句是含有情态动词的被动语态，结构为can be done。take的过去分词为taken。故填can be taken。
29．were given to by us
【解析】句意：上周五我们给了他很多礼物。根据原英语句子以及要求可知，原句子为一般过去时，改为被动语态时，谓语动词构成为was/were done，主语“Lots of gifts”为复数，因此谓语动词用were given，sth. be given to sb.“某物被给了某人”；原句子中主语“We”改变为宾语，用宾格形式us，前加by，意为“被”。故填were；given；to；by；us。
30．Should be fed
【解析】句意：这条狗应该每天投喂。句中有情态动词“should”，则将其提到句首，并注意首字母大写，且此处是含情态动词的被动语态，“be fed”照着写下来即可。故填Should；be；fed。
31．should finished
【解析】句意：学生应该按时完成作业。含有情态动词的被动语态是：情态动词+be+done，finish的过去分词是finished，故填should；finished。
32．is spoken
【解析】句意：现在很多中国人说英语。原句时态是一般现在时，所以变为被动语态后，时态仍然保持不变，一般现在时的被动语态结构是am/is/are done，主语是English，所以be动词用is，speak要变成过去分词spoken。故填is；spoken。
33．be given
【解析】句意：父母应该给孩子们更多与家人在一起的机会。题干要求是变为被动语态，且原句含有情态动词should，被动语态结构为“主语+情态动词+be done (过去分词)+其它”。“give”的过去分词是“given”。故填be；given。
34．The sick man must be sent to the hospital.
【解析】句意：我们必须把那个病人送到医院。主动语态改为被动语态时，原句的宾语the sick man作主语，原句的谓语must send改为must be sent，其它部分保持不变。故填The sick man must be sent to the hospital.
35．These children should be taught to swim by us.
【解析】句意：我们应该教这些孩子游泳。主动句变成被动句，需要将主动句的宾语“these children”变为主语，主动句的主语“We”与介词“by”构成介宾短语作被动句的状语，by后跟宾格us。原级是含情态动词的被动语态，所以该句被动语态的结构为：should be done。故填These children should be taught to swim by us.
36．be seen
【解析】句意：我们在白天看不到星星。将句子改为被动语态：将宾语变成主语，谓语动词由主动语态变成被动语态，即be动词+过去分词。原句宾语是no stars变成了该句主语，原句谓语动词see变成被动语态be seen，情态动词can后加动词原形，所以be动词填原形。故填be seen。
37．be shown/showed
【解析】句意：人们再也不需要出示行程码了。考查主动语态变被动语态。被动语态的结构为be done，原句中有情态动词needn’t，所以be动词用原形，show的过去分词为shown或者showed。故填be；shown/showed。
38．be seen
【解析】句意：春节期间，我们可以在中国的许多地方看到剪纸。分析题干，此处为含有情态动词can的被动语态，构成为：can + be + 动词过去分词，谓语动词see的过去分词为seen。故填be；seen。
39．be made
【解析】句意：当我们画卡通脸时，我们应该让脸的某些部分变大，使它看起来更有趣。空处前有should，所以此处含有情态动词的被动语态：情态动词+be done，make的过去分词为made。故填be；made。
40．be allowed
【解析】句意：我们的老师应该允许我们每天踢一小时足球。改为被动语态，可以表达为“我们应该被允许每天踢一小时足球。”，空处位于情态动词should后，变为被动形式，用be+过去分词（allowed），故填be；allowed。
41．be cleaned
【解析】句意：我们应该每天打扫教室。根据“should clean”可知，变被动语态时，谓语动词应变为“be done”的结构，故此处应变为should be cleaned。故填be；cleaned。
42．be paid
【解析】句意：如果他们想获得更高的成绩，就应该注意手写字体。实义动词变被动语态，其结构为be done。句中谓语动词pay，其过去分词为paid；因原句含有情态动词，其后的be动词应用原形，即be paid。故填be paid。
43．be swept
【解析】句意：学生们应该每天扫地。分析句子可知，原句含有情态动词should，因此要改为含有情态动词should的被动语态，结构为：情态动词should+be+动词的过去分词；谓语动词sweep的过去分词是swept。故填be；swept。
44．be done
【解析】句意：政府应该做些什么来让城市变得干净。原句是含有情态动词的结构，此处变成被动应用含有情态动词的被动结构，结构为“情态动词+be+过去分词”，故填be；done。
45．be obeyed
【解析】句意：我们必须遵守校规和交通规则。分析句子可知，本句应是含有情态动词的被动语态：情态动词（must）+be done。obey的过去分词为obeyed。故填be；obeyed。
46．be cleaned
【解析】句意：我们必须每天都打扫教室。带有情态动词的被动语态的基本结构是“情态动词+be+动词的过去分词”，clean的过去分词为cleaned。故填be cleaned。
47．needn’t written
【解析】句意：你现在不必写这封信。含情态动词的被动语态形式为：情态动词+be done；write的过去分词为written。故填needn’t；written。
48．can’t be taken
【解析】句意：学生未经允许不能把杂志带出阅览室。考查情态动词的被动语态。原句含有can’t，其被动应该为can’t be done。take的过去分词是taken。故填can’t；be；taken。
49．be encouraged
【解析】句意：我们应该鼓励学生花一些时间参加团队运动。原句宾语“school children”变为主语，与动词“encourage”之间是被动关系，此处需用被动语态。原句含有情态动词，应改为含情态动词的被动语态，其结构是should be done。encourage的过去分词为encouraged。故填be；encouraged。
50．be written
【解析】句意：我们可以把规则写出来，贴在墙上。情态动词can的被动语态构成：主语+can+be +动词过去分词，write的过去分词是written，故填be；written。
51．be written
【解析】句意：你应该把所有的答案写在答题纸上。句中answers与write之间是逻辑上的被动关系，被动语态结构为be done；句中should是情态动词，所以此处被动语态中用be动词原形；动词write的过去分词为written。故填be；written。
52．Should be
【解析】句意：青少年应该被允许选择他们自己的衣服。原句是含有情态动词的被动语态，变一般疑问句时，情态动词要放在主语前，主语后跟be done。故填Should；be。
53．be offered
【解析】句意：根据新规，所有的学校必须提供课后服务。被动语态的基本结构为：be done。情态动词后加动词原形，所以此处应用be offered，表示“课后服务必须被提供”。故填be；offered。
54．be taken
【解析】句意：我们必须照顾好我们国家的老年人。must为情态动词，因此被动语态是含有情态动词must的句子，结构为must be done。take的过去分词是taken。故填be；taken。
55．Children under 12 years old should not be allowed to leave at home alone.
【解析】句意：12岁以下的儿童应该被允许单独留在家里。原句是含有情态动词的被动语态，变成否定句，只需在情态动词后加not，故填Children under 12 years old should not be allowed to leave at home alone.
56．Students should not be allowed to do homework with friends
【解析】句意：应该允许学生和朋友一起做作业。根据题意是变成否定句，should“应该”，是情态动词，后加动词原形，变成否定句在情态动词后直接加not。此处是含有情态动词的被动语态，故答案为：Students should not be allowed to do homework with friends。
57．cannot be planted
【解析】句意：你不能在干燥的土地上种树。改为被动语态：“树木不能被种植在干燥的土壤中”，应用含有情态动词的被动语态：can be done，此处是否定句，情态动词can后加not。故填cannot be planted。
58．be kept
【解析】句意：我们必须把食物放在冰箱里，这样它就不容易坏了。根据题目要求可知，需要用be done的格式，结合must，后接动词原形，keep的过去分词是kept；故填be；kept。
59．be made
【解析】句意：学生们应该为暑假做计划。情态动词的被动语态的构成形式为：情态动词+be+ done；make的过去分词是made。故填be；made。
60．be shared
【解析】句意：我们可以共享很多东西，比如自行车、汽车和雨伞。原句含有情态动词can，改为被动语态的结构为：can+be+动词的过去分词，“share”的过去分词是shared。故填be；shared。
61．be taught
【解析】句意：我们应该教学生一些必要的生活技能。根据题干要求，将原句改成被动句，此处为含情态动词should的被动语态，其结构是should be+done；teach“教”，是动词，其过去分词是taught。故填be；taught。
62．can’t be
【解析】句意：没有人能回答这个问题。含情态动词can的被动语态构成：主语+can+be+动词过去分词，由“anybody”可知，句子应是否定句，情态动词用can’t，故填can’t；be。
63．be held
【解析】句意： 下周五我们将举行班会，讨论团队合作。由时间状语“next Friday”可知，句子时态为一般将来时，因此要改为一般将来时的被动语态，其结构为：will+be+动词的过去分词；hold的过去分词为held。故填be；held。
64．be kept
【解析】句意：我们必须每天保持教室干净整洁。主动语态含有情态动词must，变为被动语态时，要改为含有情态动词的被动语态，其结构为：情态动词+be+done，句子谓语是keep，其过去分词为kept。故填be；kept。
65．be kept
【解析】句意：我们必须保持噪音低于50分贝。考查主动句改被动句。被动句的结构是be done。must后接be动词原形，keep的过去分词形式是kept。故填be；kept。
66．Many of the stars can’t be seen by us.
【解析】句意：我们不能看见很多星星。改为被动语态：“we”是原句动词“see”的施动者，受动者是“many of the stars”，变为被动语态后二者角色需互换，基本结构为“受动者+情态动词can’t+be +过去分词+（by+施动者）+其他”，故填Many of the stars can’t be seen by us.
67．be organized
【解析】句意：他们在两周后组织一个英语演讲比赛。原句包含情态动词，其被动形式为：情态动词+be done，done为动词对应的过去分词。organize动词，“组织”，其过去分词为organized。故填be；organized。
68．be finished
【解析】句意：你必须按时完成工作。句子的主语是“The work”，“工作”与动作“完成”之间是被动关系，用“情态动词+被动结构”。 表达“必须被完成”用“must be finished”。故填be；finished。
69．needn’t be done
【解析】句意：你不必现在做它。根据“needn’t”可知，need是情态动词，含情态动词need的否定形式的被动语态构成：主语+needn’t+be+动词过去分词，do的过去分词done，故填needn’t；be；done。
70．should be encouraged to
【解析】句意：教师应该鼓励学生说出自己的想法。改为被动语态就是说“学生应该被鼓励说出自己的想法”，“应该被做……”是should be done，这里是“被鼓励去做……”，也就是be encouraged to do…。故填should be encouraged to。
71．must be stopped from
【解析】句意：父母必须阻止孩子玩过多的电脑游戏。改为被动语态就是说“孩子必须被阻止玩过多的电脑游戏”；“必须被做……”是must be done；短语“被阻止做……”是be stopped from doing…。故填must be stopped from。
72．can’t be sold
【解析】句意：商店不能向青少年出售香烟。改为被动语态就是说“香烟不能被销售给青少年”，“不能被做……”是can’t be done；动词“销售”sell的过去分词是sold。故填can’t be sold。
73．Should be
【解析】句意：应该把会议的情况告诉他。题干中含有情态动词should，变一般疑问句要把情态动词提到句首，在句首首字母大写。故填Should；be。
74．be given
【解析】句意：你必须在周五之前把字典还了。 根据含有情态动词的被动语态结构是：情态动词+be+过去分词；故填 be ； given。
75．Must be returned
【解析】句意：你必须按时还书。根据含有情态动词的被动语态结构是：情态动词+be+过去分词；疑问句把情态动词must提前；故填(1). Must (2). be (3). returned。
76．be put
【解析】句意：我们必须把用过的电池放进这些绿色的箱子里。改后的句子是含有情态动词的被动语态，用“情态动词+be done”结构表示，put的过去分词还是put，故填be put。
77．should be made
【解析】句意：你应该每天整理床铺。含有情态动词的被动语态结构是：情态动词+be+过去分词。故填should；be；made。
78．can’t be seen
【解析】We can’t see stars in the day time. (改为被动语态) 根据含有情态动词的被动语态结构是：情态动词+be+过去分词；故填(1). can’t (2). be (3). seen
79．be written
【解析】句意：汤姆应该给他的老板写一封回信。根据“should”及题干要求可知，此处改为含有情态动词的被动语态，结构为should be done，write的过去分词是written，故填be；written。
80．The noise must be kept under 50dbs here./The noise here must be kept under 50dbs.
【解析】句意：我们在这儿必须把声音控制在50分贝以下。含情态动词的被动语态结构为：情态动词+be done。原句动作承受者the noise提到句首作主语，keep的过去分词为kept，地点状语here的位置可灵活处理，故填The noise must be kept under 50dbs here./The noise here must be kept under 50dbs.
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