情态动词表推测用法总结及专项练习
1.can / could用于表推测的用法
(1) 从使用句型上看，can 通常只用于否定句或疑问句，一般不用于肯定句，而could 可用于肯定句、否定句和疑问句。两者没有时间上的差别，只是could 比 can 更委婉，更不确定。如：
It can’t [couldn’t] be true. 那不可能是真的。
What can [could] they be doing? 他们会在干什么呢?
We could go there this summer. 今年夏天我们可能要去那儿。
注：can 有时也用于肯定句中表示推测，主要用于表示理论上的可能性(即从理论上看是可能的，但实际未必会发生)，或表示“有时”之意。如：
Even experienced teachers can make mistakes. 即使是有经验的教师也可能出错。
She can be very unpleasant. 她有时很令人讨厌。
(2) 从时间关系看，对现在或将来情况作推测，后接动词原形；对正在进行的情况作推测，后接 be doing 结构；对过去情况作推测，后接动词完成式。如：
He could have gone home. 他可能已经回家了。
He can’t [couldn’t] have understood. 他不可能理解了。
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Why does he know this? Can [Could] someone have told him about it? 他怎么知道? 会是哪个人告诉他了吗?
(3) “could+完成式”除表示对过去的推测外，还有以下重要用法：
① 表示过去没有实现的可能性，常译为“本来可以”。如：
I could have lent you the money．Why didn’t you ask me? 我本来可以借这笔钱给你的。你为什么不向我提出?
② 用来委婉地责备某人过去应该做某事而没有去做，常译为“本来应该”。如：
You could have helped him. 你本来应该帮助他的。
③ 表示“差点儿就要”。如：
I could have died laughing. 我差点儿笑死了。
2. may / might用于表推测的用法
表示推测，两者都可用，只是 might 比 may 语气更不确定，表示的可能性更小。
(1) 在句型使用方面：两者均可用于肯定句和否定句，但用于疑问句时，may通常不用于句首，但可用于疑问句的句中（如特殊疑问句等），而might尽管可以用于疑问句的句首，但不算普通，通常会改用其他句式（如用could等）。如：
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He may [might] know the answer. 他可能知道答案。
He may [might] not believe you. 他可能不会相信你。
And who may [might] she be? 那么她会是哪一位呢？
(2) 从时间关系看，对现在或将来情况作推测，后接动词原形；对正在进行的情况作推测，后接 be doing 结构；对过去情况作推测，后接动词完成式。如：
He may [might] tell his wife. 他也许会告诉他妻子。
He may [might] be writing a letter. 他可能在写信。
She may [might] have read it in the papers. 她可能在报上已读到过此事。
(3)“might+完成式”除表示对过去的推测外，还有以下重要用法：
① 表示过去某事可能发生而实际上却并没发生。如：
It was really very dangerous. I might have killed myself. 那真的是太危险了，我差点没命了。
A lot of men died who might have been saved．很多人本来可以获救的却死了。
② 表示委婉的批评或责备。如：
You might have made greater progress. 你的进步本来可更大一些的。
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You might at least have answered my letter. 你至少可以回我一封信嘛。
3. must表示推测的用法
must 表示很有把握的推测，其意为“一定会”“肯定会”，只用于肯定句，一般不用于否定句或疑问句。表示对现在或未来的情况作推测，后接动词原形；表示对过去情况的推测，接动词完成式。如：
I must be the happiest woman on earth! 我一定是世界上最幸福的女人了。
No, he must be lying. 不，他一定在撒谎
He must have mistaken my meaning. 他一定误会了我的意思。
4. should have done 的用法
should have done只用于谈论过去情况，主要有两个用法：一是用于推测过去已经发生的情况，二是用于指本该发生而实际上未发生的情况。如：
You should have told me so before. 你早就应该告诉我。
He should have arrived by now. 此时他本该到了。
Look at the time! We should have been at the theatre ten minutes ago. 瞧都什么时候了! 十分钟前我们就该到戏院了。
5. need have done 的用法
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need have done结构主要用于否定句或疑问句，一般不用于肯定句。用于否定句时，表示本来不必做某事，但实际上却做了；用于疑问句时，用于询问某一过去动作的必要性。如：
You needn’t have hurried. 你当时实在不必那么匆忙。
She needn’t have come in person — a letter would have been enough. 她本不必亲自来——写封信来就足够了。
Need you have paid so much? 你当时真须要付那么多钱吗?
Need they have sold the farm? 他们那时非得把农场卖掉不可吗?
历届NMET中表推测的情态动词的用法
情态动词是中学英语学习中的一个重点和难点，也是高考的重点考察内容之一。其中表示推测用法的情态动词在近几年的高考中更是屡见不鲜。现结合近几年的高考题目，对表推测的情态动词的用法作一归纳，希望对各位考生会有所帮助：
【考例】1. Naturally, after I told her what to do, my daughter _____ go and do the opposite!
A. may B. can C. must D. should
(2003年普通高等学校春季招生统一招生考试英语试题（安徽卷）)
【分析】Can,may,must都可用来表示”推测”，但侧重点各有不同：
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May常用来指”事实上的可能性”，而can则表示一种”理论上的可能性”例如：
The railways may be improved.
=It is possible that the railways will be improved.
=Perhaps/Maybe/Possibly the railways will be improved.
铁路可能会得到改进。（意味着已有具体的改进计划或方案。）
The railways can be improved.=It is possible for the railways to be improved.
铁路可以得到改进。（意思是铁路还不完善，尚有问题存在。）
理论上的可能性(can)比事实上的可能性(may)更弱。
在一般的陈述句，can与sometimes几乎相同，表示一种偶然的可能性。比如：
Even expert drivers can make mistakes.甚至是很熟练的驾驶员也可能会犯错。
=Even expert drivers sometimes make mistakes.
=It is possible for the expert drivers to make mistakes.
因此，如果讲的是一种特殊情况，不是一般情况，就用may,试比较：
Mr Reed looks pale.He may be ill.
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Mr Reed is in poor health.He can be ill at any time.
Must指逻辑必然,作“想必”、“准是”、“一定”解，用来表示我们对某事有把握的推论或揣测。（考虑到迹象如此，再无别的结论=It seems certain that….）:
They must be very tired now, for they have been working the whole morning.
他们现在一定是非常累了，因为他们整个上午都在工作。
析：填C.must。意思是”不出所料，当我告诉女儿要做的事时，她准会去做相反的事。”
【考例】1、Mary ___ be in Paris.I saw her in town only a few minutes ago.(NMET1994)
A.mustn’t B.shouldn’t C.can’t D.may not
2、.--Is John coming by train? (NMET 2002 Tianjing )
--He should,but he ___ not.He likes driving his car.
A．must B.can C.need D.may
【分析】May用于否定时，not不是否定may，而是否定句中的动词，这一点与can不同，试比较：
He may not know the truth.他可能不知道事情的真相。（=It is possible that he didn’t know the truth.）
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He cannot know the truth.他不可能知道事情的真相。
must表示推测的这种用法通常用在肯定句中，在疑问句中常用can(可能)，在否定句中常用can’t(不可能，不会是)，而不用mustn’t。例如：
--- Somebody is knocking at the door. Who can it be ? It must be Wang Hong.
--- No, It can’t be Wang Hong, because she left for Shanghai this morning.
---有人在敲门。会是谁呢？一定是王红。
---不，不会是王红，因为她今天早晨就动身去上海了。
因而You must be joking.在意义上相当于You can’t be serious.
析：1、填C。意思是”玛丽不可能在巴黎。几分钟前我还看见她在镇上。2、填D。意思是”--约翰会坐火车来吗？--应该会，但他可能不会。他喜欢开车。”
【考例】1.---I heard they went skiing in the mountains last winter. (NMET 2002Beijing )
---It ___ true because there was little snow there.
A.may not be B.won't be C.couldn't be D.mustn't be
【分析】Could,might表示过去的可能性。
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I thought it might be true.我本认为那是真的。
He could be very unreasonable.他有时可能毫不讲理。
析：填C。它是对去年冬天所发生的事进行评价。
【考例】1.--Are you coming to Jeff’s party? (NMET 2000)
--I’m not sure.I_____go to the concert instead.
A.must B.would C.should D.might
2.---Look!The clouds are gathering.
---Yes.I'm afraid it _____ be pouring down soon.
A,can B,must C,should D,might
【分析】could和might表示现在的情况时，更带有不肯定性和慎重味道，构成礼貌或婉转说法，包含或许的意思：
A:I wonder where Tom is. B:He may/might/could be in the library.(Perhaps he is in the library.)
因此在wonder, fear,be afraid等后接的从句中,通常用may/might/could,表达一种探询的观点：
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I was afraid you might be out of sorts.我怕你可能心情不痛快。
假设性的可能和试探性的可能，也用could和might：
Our team might still win the race.(可以意译为：It is possible,though unlikely,that ……)
析：1、2均填D.might
【考例】Mr. Bush is on time for everything. How _________ it be that he was late for the opening ceremony? A．can B．should C．may D．must
(2001年上海普通高校春季招生考试试卷)
【分析】表示推测的may通常不用于一般疑问句，而要用can代替。Can用于一般疑问句时，还可表示惊讶或怀疑，意思是”（到底）可能有这样的事吗？”，比如：
“There is the doorbell.””Who can it be at this time of day?”有人按门铃。””这个时候到底会是谁呢？”
Must也偶尔用于疑问句：Must there be some good reason for the delay?这个问句设想的是一个肯定的回答，可以解释为”Does there have to be some good reason……?”
may可用于特殊疑问句或wh-从句，意思是”（到底）是…”、”不知是否…”：
I wonder what it may mean.我不知道这究竟是什么意思。
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How old may his father be?他父亲到底有多大年纪？（比How old is his father?委婉的说法。）
析：填1、A.can.（布什先生做什么事都很按时。他怎么可能会在开幕式上迟到呢？）
【考例】1. Sorry I'm late. I ________ have turned off the alarm clock and gone back to sleep again.( 2000年普通高等学校春季招生考试 (北京、安徽卷)
A. might B. should C. can D. will
2.─There were already five people in the car but they managed to take me as well.
─It __ a comfortable journey. (NMET95)
A.can't be B.shouldn't be C.mustn't have been D.couldn't have been
【分析】“情态动词have + -ed分词”结构可以表示对已发生的事情进行推测, 就表示的可能性程度而言，must最大，could其次，may更次之，might最小。
must + have + -ed分词: 用于肯定句, 表示推测过去某事“肯定,一定，准是”发生了。 其否定形式为：can’t / couldn’t have v-ed, 表示过去不可能发生某事。 may(might) + have + -ed 分词: 用于肯定句和其他否定句, 表示对已发生事情的不肯定的推测, 意为“可能, 大概”, 其中might较may语气更弱, 把握更小。Can/could用于否定或疑问句中,表示对过去发生的事件的“怀疑或不肯定”。could 比can更表示说话人语气的不肯定。例如：
I mailed that letter a week ago. He must have received it.我一周前就发出了那封信, 想必他一定收到了。
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I can’t find my keys. I may / might have left them at the school yesterday.
Jack can’t have arrived yet,otherwise he would have telephoned me.（上海1997）
It couldn't have been Mr. Smith. He has gone to China.不太可能是史密斯先生。他已去了中国。
另外，注意may不可用于疑问句，它的这种功能已为can所取代。例如Can they have missed the bus?的答句是：Yes,they may have done.而不是Yes,they can have done.这一点要注意。
Must偶尔也能用于否定句：His absence must not have been noticed.此句和His absence can’t have been noticed.的意思是一样的。许多评论者认为这类句子是不可能成立的，但它们正在为越我来越多的人所接受和使用，在美国英语中尤其如此。
对正在发生的事情进行推测，则采用”情态动词+be+现在分词”结构，其中情态动词的区别与上相同。
析：答案A、D。can通常不用于肯定句表猜测；”should+have+-ed分词”表示”过去本来应该做……”，但实际上没有做，意思是”本该…..”，带有责备口气:I was really anxious about you.You shouldn’t have left without a word. (NMET2001) ；”will+have+-ed分词”只是将来完成时的一种形式。
【考例】1.It's nearly seven o'clock. Jack ____be here at any moment. (NMET95)
A.must B.need C.should D.can
【分析】should(ought to)表示很可能、预期的意思，指一种尝试性推论，可认为是must的语气较
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弱的对应词，意思是”应该会、一定。。。吧”。试比较：
Our guests must be home by now.(‘I am certain’)我们的客人现在一定到家了。（根据他们动身的时间、路程远近、速度等具体条件，我能断定/肯定他们现在已经到家了。）
Our guests should(ought to) be home by now.(‘They probably are,but I’m not certain.)我们的客人现在该到家了。（含义是我想他们很可能到家了，但我不能肯定”）
与must不同还在于它常常表示将来：
--When can I come for the photos?I need them tomorrow afternoon.
--They_____be ready by 12:00. (NMET1998) A.can B.should C.might D.need
表示不太可能可用shouldn’t(oughtn’t to):
There shouldn’t(oughtn’t to) be any difficulties.不该有任何困难。
析：填C。意思是”将近七点了。杰克很可能随时会到。” 另外，在近几年的NMET中，对情态动词及其它语法项目的考查均放到一定的语境中进行，要求考生利用所学英语各项基础知识进行初步的语言运用，而不再是单纯的语法知识题和短语题。这类试题往往通过题干的其他部分或附加句子提供某个信息，然后让考生根据这个信息进行合理推理，产生新的想法和认识。因此，在做这类题时，除要熟悉所考查的语法规则外，还要认真分析句子的结构，注意抓住关键词，分析上下文的逻辑关系。不能单凭语法规则做题。
巩固练习
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1.Michael __ be a policeman, for he's much too short.
A. need't B. can't C. should D .may
2.Johnny,you __ play with the knife. You __hurt youself.
A.won't,can't B.mustn't,may C.shouldn't,must D.cant't,shouldn't
3.Peter __ come with us tonight,but taken he isn't very sure yet.
A.can B.may C.will D.must
4.Put on more clothes.You __ be taken feeling cold with only a shirt on. A.must B.can C.could D.would
5.It's nearly seven o'clock.Jack __ be here at any moment.
A.must B.need C.should D.can
6.I didn't hear the phone.I __ asleep.
A.must be B.must have been C.should be D.should have been
7.Jack __ yet,otherwise he would have telephoned me.
A.mustn't have arrived B.shouldn't have arrived C.can't have arrived D.need not have arrived
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8.--there were already five people in the car but they managed to take me as well. --It __ a comfortable journey.
A.can't be B.shouldn't be C.mustn't have been D.couldn't have been
9.He __you more help,even though he was very busy.
A.might have given B.might give C.may have given D.may give
10.Yesterday Jane waooked away from the discussion.Otherwise,she __ something the would regret later.
A.had said B.said C.might say D.might have said
11.There was plenty of time.She __.
A.mustn't have hurried B.needn't have hurried C.should have written it out D.couldn't have hurried
12.Tom ought not to __ me your secret,but be meant no harm.
A.have told B.tell C.be telling D.haven't told
13.I told Sally how to get there ,but perhaps I __ for her.
A.had to wirte it out B.must have written it out C.should have written it out D.ought to write it
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out
14.If you had worked harder,you __.
A.would succeed B.had succeeded C.should succeed D.would have succeeded
15.--If he __,he __that food. --luckily he wsa sent to the hospital immediately.
A.was warned;would not take B.had been warrned;had not taken C.would be warned;had not taken D.would have been warned;had not taken
16.--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
17.Sorry I'm late.I __ have turned off the alarm and gone back to sleep again.
A.might B.should C.can D.will
18.--Shall I tell John about it? --No you __.I've told him already. A.needn't B.wouldn't C.mustn't D.shouldn't
19.The new airoprt __ if they had not stopped working on it.
A.would complete B.had been completed C.had completed D.would have been completed
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20.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
21.That 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
22.Susan __ written a report like this.
A.can have B.mustn't have D.can't have D.ought to not have
23.There wasd a lot of fun at yesterday's party.You __ come,but why didn't you? A.must have B.should C.need have D.ought to have
[答案及难点解析] 1.B 2.B mustn't表示“禁止”，may表示“不可能” 3.B can表示“理论上的可能、普遍性的可能、当然的可能，并非说话人主观认为可能，即并非猜测”，故不可选A。4.A 5.C at any moment/minute意为“随时，马上”。 6.B 由句中的时态可知是在对过去的事件进行推测，故用情态动词+have done。7.C 由otherwise…一句可知说话人对Jack没有来持确定的态度。除所给答案外，A也正确。 8.D与7题相似，C也是正确的，意为“肯定不舒服”。 9.A may不可表示过去的事。 10.D 11.B表示“当时本没必要那么匆忙”。 12.A 13.C 14.D 15.B 16.A二人相遇的可能性不大。17.A18.A19.D对过去情况的虚拟假设，注意要用被动语态。20.D21.D22.C据常识可知是在对过去的事进行推测。23.D
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