第五章 情态动词和虚拟语气
一、情态动词的语法特征
(1)情态动词不能表示正在发生或已经发生的事情，只表示期待或估计某事的发生。
(2)情态动词 除ought 和have 外，后面只能接不带to 的不定式。
(3)情态动词没有人称，数的变化，即情态动词第三人称单数不加-s。
(4)情态动词没有非谓语形式，即没有不定式、分词、动名词等形式。
二、虚拟语气用来表示说话人的主观愿望或假想，所说的是一个条件，多半不是事实，或与事实相反。
高考重点要求：
1、情态动词的基本用法
2、情态动词表示推测的语义差别
3、情态动词后接不定式完成体的不同意义
4、虚拟语气中情态动词的用法
第一节 知识点概述
一、情态动词
（一）情态动词种类
1. can表示体力或脑力方面的“能力”、“技能”或根据客观条件能做某种动作的“可能性”, 但表示人的体力或智力的具体动作时须用 be able to .
He was able to do that without any help.他不需要任何帮助就能完成这项工作。
2. may表示“允许，可以”，相当于be allowed to .
may或might可和as well连用，表示“建议”，译为“还是……的为好”
You may as well keep a certain distance from that mad man. 你们还是离那疯子远点为好。
You might as well go home now.你还是现在回家为好。
3. must表示“必须”或“应当”、“一定”。
4. have to 加动词原形，表示“不得不”，“必须”，它比must更强调客观。
Tom had to work into the deep night every day to earn a living. 汤姆为了生计每天都得工作到深夜。
5. should 表示“劝告”，“建议”或“义务”时，译作“应当”，或表示“预测”和“可能”。
He should take care of his parents as they are old enough not to live on themselves. 由于父母亲老了，不能自理，他应当照顾他们。
He should be there now. 他应该在那儿。
should have done在虚拟语气中表示“责备或后悔”。
6. ought ，只有一种形式，且ought后必须加to，然后跟接动词原形表示“有义务”或“必要”做某事，译为“应当，应该”。
7. dare 可以用作情态动词，后面跟不带to的动词不定式，这主要用于否定句中，它本身可有现在时第三人称单数，词尾加s，它还可以有ing分词形式(daring)和过去式及ed分词形式(dared)。
（二）情态动词在一般时否定句中的用法
can't(cannot) 表示“不可能”， may not 表示“不可以”， mustn't(must not) 表示“一定不要”，“不许可”，needn't (need not) 表示“不必”，dare not ＋动词原形表示“不敢”。
He can't finish his essay by this time. 现在他不可能写完论文。
He may not sleep now. 他或许现在没在睡觉。
You mustn't criticize her in that way. 你不应那样批评她。
You needn't come tomorrow. 你明天没必要来了。
He dared not meet his fiancée. 他不敢见女朋友。
（三）can，may，must三者用法比较
can，may，must是三个最重要的情态动词，其基本句型如下：
肯定句：主语+can，may，must +动词原形
否定句：主语+can，may，must +not +动词原形
疑问句：Can，May，Must +主语+动词原形
1. can，may，must的肯定句
You may eat lunch，but you must wash your hands.
你可以吃饭，但是你必须洗手。
（1）can
a.表示能力；能，会
She can run fast，but I can't.
她很会跑，但是我不会。
b.表示可能；能够
I can get there in ten minutes.
我十分钟之后就可以到那儿。
（表示一种可能性）
c.表示允许；许可
You can use this dictionary.
你可以用这本字典。
d.can和be able to比较
can只有现在式和过去式，而be able to可以用于各种时态。
can（could）表示能力时，可用be able to代替。
I can（=am able to）pay for the book. 我买得起那本书。
He will be able to tell you the news soon. 他很快就能告诉你消息了。
She has been able to come to school. 她已经能去学校了。
（2）may
a.表示请求、许可
May I borrow your pen？
我可以借你的钢笔用一用吗？
b.可能、或许
Tomorrow I may go shopping.
明天，我可能（或许）去商店买东西。
He might be our new teacher.
他或许是我们的新老师。
（3）must
a.必须、应该（表示有做某一动作的必要或义务）
You must buy a ticket.
你必须买一张票。
b.一定、准是（表示有把握的判断或推测，一般只用于肯定句中）
在You must这一句型中，它的意思与祈使句相同。
You must get up early. =Get up early.
你必须早起。
You must study hard. =Study hard.
你必须用功读书。
He must be our new teacher.
他肯定是我们的新老师。
2.表示推测的用法
can , could ,may ,might ,must 皆可用来表示推测，其用法如下：
a．could ,might 表示推测时不表示时态，其推测的程度不如can ,may。
b．can ,could 用于否定句和疑问句中。
句型：主语+ can't , couldn't +be +动词ing．（否定句）
Can ,Could +主语 +be +动词 ing．（疑问句）
They can't be cleaning the room now．他们现在不可能在打扫房间。
c．may ,might , must 用在肯定句中。
句型：主语+ may ,might ,must +be +动词 -ing
（表示对现在发生动作的推测）
He must be sleeping . 他现在肯定在睡觉。
d．但如果上述这些词 (must ,can't… ) + have +过去分词则指对过去已发生的事进行推测。
The road is wet. It must have rained last night .
地是湿的；昨天晚上肯定下雨了。
There isn't any water on the road . It (can't ) couldn't have rained last night .
地面上一个水滴都没有，昨天不可能下雨了。
（四） have to的用法
1. have（has）to +动词原形
have（has）to后面要用动词原形。当主语为第三人称单数时用has to，当句子是过去时用had to。
We have to leave now.
我们不得不现在就离开。
He has to work on Sunday.
他不得不在周日工作。
I had to do my homework last Sunday.
上周日，我不得不做作业。
2. have to的否定句
句型：主语+don't（doesn't, didn’t, will not）have to+动词原形
You don't have to walk so fast.
你不必走那么快。
He will not have to buy a new coat next year.
明年，他没必要买新外衣了。
3. have to的疑问句
句型：Do（Does, Did, Will）+主语+have to +动词原形？
Do you have to study maths now？
你现在必须学数字吗？
Yes，I do.是的，必须学。
No，I don't（have to）。不，不必学。
Did he have to ask the question？
他非要问那个问题吗？
Yes，he did.是的。
No，he didn't（have to）.不。
4. must与have to比较
must侧重于个人意志和主观上的必要，have to侧重于客观上的必要。如果用于过去时态或将来时态时，则要用have to的相应时态来代替must。但must可用于间接引语中表示过去的必要或义务。
My brother was very ill，so I had to call for the doctor in the middle of the night.
我弟弟病得很厉害，我只得半夜里把医生请来。（一般过去时）
I haven't got any money with me，so I'll have to borrow some from my friend.
我身上没有钱，只好向朋友借点了。（一般将来时）
He said that they must work hard.他说他们必须努力工作。
二、虚拟语气
虚拟语气表示说话人的意愿、假设、猜测或建议。虚拟语气不表示客观存在的事实，谓语动词用特殊的形式表示虚拟语气。
1． 表示与现在事实相反时的谓语形式。
从句 主句
过去式 (be和were) would (should、could)+ 动词原形
例如：If Tom were hungry, he would eat the bread. (In fact, Tom isn’t hungry.)
2． 表示与过去事实相反的谓语形式。
从句 主句
had + 过去分词 would (should、could) + have +过去分词
例如：If I had left a little earlier, I would have caught the early bus. (In fact, I didn’t catch the bus.)
3． 表示与将来事实相反的谓语形式。
从句 主句
动词过去式
should + 动词原形
were to + 动词原形
would (should、could) + 动词原形
例如：If they came tomorrow, we would told them about it. (In fact, they won’t come tomorrow。)
4． 动词wish后的宾语从句中，谓语动词可用过去式、过去完成式或would、might加原形。
例如：I wish I were as strong as you.
He wished I would stay with us.
She wished I had attended the meeting yesterday.
5． 在有些动词如：suggest、insist、order等动词后，从句谓语动词用“should + 动词原形”，should可以省略。例如：
He suggested that we (should) discuss the problem right now.
6． 在有些句型中如：It is important (necessary、natural、strange等) + that从句中的谓语动词用should + 动词原形，should可以省略。例如：
It is necessary that the doctor (should) be sent there at once.
7． 在It is time that, I would rather that句式中从句谓语动词用过去式。例如：
It is time we went to bed.
I would rather he came next week.
第二节 实战演练
一、复习时需注意的要点
（一）情态动词
1、情态动词在句中没有人称和数的变化。
2、含有情态动词的句子改为否定句或疑问句不必加助动词，只需要将情态动词置于主语前，或在情态动词后加上not。
例如：Must I write a letter to cheer him up?
You needn’t wait for me.
3、 情态动词的过去式，例如can-could，may-might。但是少数情态动词只有过去式，例如used to表示过去常常。must的过去式往往用had to代替。
4、 情态动词后还可接不定式的进行式、完成式和被动式。
例如：He can’t be doing his homework now. 他现在不可能在做功课。
He must have attended the meeting last night. 昨晚他一定参加了会议。
（二）虚拟语气
1、 在if条件句中，如果含有were , should或had等助动词，if可以省去，句子用倒装。
例如：Were I you , I would buy this reference book.
2、 should与would都可以用于if条件句的主句中，但should一般只用于第一人称，would用于所有人称。
例如：If you were here , I would tell you the news .
3、 某些条件可以用介词短语without… , but for 等来表示 。
例如：Without your help , I could not have succeeded in passing the exam .
4、 有时句子通过but或otherwise等词来表示真实与虚拟的转换，在这种情况下，只有不真实的部分用虚拟式。
例如：I was ill yesterday；otherwise I would have played football with you .
But for the heavy rain , we would have gone to the concert .
5、 有suggest等词的相应的名词组成的同位语从句及表语从句用虚拟式。
例如：I accepted my mother’s suggestion that I should eat an apple every day .
二、历届高考试题分析
例1、There ____ be any difficulty about passing the road test since you have practised a lot in the driving school.
A. mustn’t B. shan’t C. shouldn’t D. needn’t
答案：C
【解析】 根据经验或惯例对某一情况进行推测，用should或ought to，常译成“按理应该…”或“可能会……”。shouldn’t是其否定形式。
例2、-Is John coming by train?
-He should, but he _______ not. He likes driving his car.
A. must B. can C. need D. may
答案为D。
【解析】 come, go, leave, start等趋向动词的进行时表示将来时，所以答语是对这一将来动作做出的推断。may not“可能不；不一定”，根据he likes driving his car可以看出John可能乘火车来，也可能自己开车来。may not正好符合这一语境。must not“不准”；cannot“不可能”；need not“不必”。
例3、It is hard for me to imagine what I would be doing today if I _______ in love, at the age of seven, with the Melinda Cox Library in my hometown.
A. wouldn't have fallen B. had not fallen
C. should fall D. were to fall
答案为B。
【解析】 根据句意和I would be doing可以判断这是虚拟语气。at the age of seven 是表示过去的时间状语，if从句中的谓语要用had not fallen，表示对过去情况的假设。由于主句中的谓语表示对现在的虚拟，条件句中的谓语表示对过去情况的虚拟，增加了试题的难题，但是，使用排除法可以容易地做出该题：should fall 和were to fall都可以用于条件句中表示对将来的虚拟；wouldn't have fallen不用于条件句中，所以都不能作为答案。译文：如果我不在七岁时就迷恋上了我们家乡的Melinda Cox图书馆，我真不能想象我今天会做什么。
例4、You can't imagine that a well-behaved gentleman ________be so rude to a lady.
A. might B. need C. should D. would
答案为C。
【解析】 should用于表示感情，意向等句中的that从句，表示“竟然……，居然……”的惊讶，出乎意料。译文：你难以想象一位行为体面的绅士会对一位女士那么粗鲁。
例5、What would have happened ________, as far as up to the river bank?
A. Bob had walked farther B. if Bob should walk farther
C. had Bob walked farther D. if Bob walked farther
答案为C。
【解析】 因为主句的谓语动词用了would have happened，所以从句的谓语动词要用过去完成时。在虚拟语气中，如果条件状语从句中的if省略，该句要倒装。译文：如果鲍勃走得远一点，走到岸边，会发生什么事呢?
例6、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
答案为A。
【解析】 can表示可能性的推测，常用于疑问句或否定句中；may表“可能性”常用于肯定句或否定句中；must常用于肯定句中表推测，“一定……”的意思。注意：can not表示“不可能”，而may not表示“或许不……可能不……”，两者语气上有区别。译文：布什先生按时做好一切事。他来参加开幕式迟到了可能会是什么样的情景呢?
例7、My sister met him at the Grand Theatre yesterday afternoon, so he _________ your lecture.
A. couldn't have attended B. needn't have attended
C. mustn't have attended D. shouldn't have attended
答案为A。
【解析】 “情态动词+不定式完成式”有各自的含义。must have done表示对过去事情的肯定推测，多用于肯定句中；needn't have done表示过去本不必做的事情；shouldn't have done表示过去做了不该做的事情；can't (couldn't) have done表示对过去的否定性推测，意为“不可能”。所提供的情境My sister met him at the Grand 表示他不可能参加讲座。
例8、He hesitated for a moment before kicking the ball, otherwise he_________ a goal.
A. had scored B. scored C. would score D. would have scored
答案为D。
【解析】 根据otherwise可以判断出要用虚拟语气。表示过去发生的事要用would have scored。译文：在踢球前他犹豫了一会儿，否则他就会射中球门。
例9、Oh, I'm not feeling well in the stomach. I _______ so much fried chicken just now.
A. shouldn't eat B. mustn't have eaten C. shouldn't have eaten D. mustn't eaten
答案为C。
【解析】 just now是表示过去的时间状语。情态动词在表示过去发生的事时，必须用“情态动词+have+过去分词的形式”。所以只能在选项B或C中确定答案。mustn't have eaten是一个错误选项，因为“mustn't+动词”表示“禁止”，不表示判断或推测。译文：噢，我觉得胃不舒服。我刚才不应该吃那么多炸鸡。
例10、I was really anxious about you .You_________ home without a word.
A. mustn't leave B. shouldn't have left
C. couldn't have left D. needn't leave
答案为B。
【解析】 should' t have done表示本来不应该做而做了，含责备意味。译文：我真为你着急，你不应该不说一句话就离开了家。另外注意mustn't+动词表示“禁止”。
第三节 巩固练习
Direction: Beneath each of the following sentences there are four choices marked A. B. C and D. Choose the best answer that completes the sentence.
1. -Isn' t that Ann's husband over there?
-No, it _______ be him . I'm sure he doesn't wear glasses.
A. can't B. must not C. won't D. may not
2.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
3. He you more help, even though he was very busy.
A. might have given B. might give
C. may have given D. may give
4. - I help you with some shoes, madam?
-Yes, I would like to try on those brown ones.
A. Will B. Should C. May D. Must
5. The reason why they leave wasn't explained to us.
A. had B. had to C. must D. might
6. I searched for my wallet and it wasn't there. I thought I it at home.
A. left B. have left
C. might have left D. could have left
7. I asleep because it took me a long time to realize that the telephone was ringing.
A. could have fallen B. should have fallen
C. must have fallen D. mustn't have fallen
8. The only thing that really matters to the children is how soon they return to their school.
A. can B. must C. have to D. ought to
9. I want to go to the chemist's, but you go with me.
A. need not B. must not C. need D. can’t
10. I thought it over, but come to no conclusion.
A. can B. could C. should D. would
11. What we get seems better than what we have.
A. can B. could C. can't D. couldn't
12. -My goodness! I've just missed the train.
-That's too bad. I am sure you it, if you had hurried.
A. could have caught B. had caught
C. would catch D. could catch
13. Look! What you've done! You more careful.
A. may be B. had to
C. should have been D. would be
14. I repeat the question?
A. Shall B. Will C. Do you want that D. Do
15. Professor Li, many students want to see you. they wait here or outside!
A. Do B. Will C. Shall D. Are
16. You read that book if you don't want to.
A. haven't B. can't C. mustn't D. needn't
17. Johnny, you play with the knife; you hurt yourself.
A. won't… can't B. can't…shouldn't
C. shouldn't…must D. mustn't…may
18. It's nearly seven o'clock. Jack be here at any moment.
A. must B. need C. can D. should
19. -There were already 5 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. couldn't have been D. mustn't have been
20. Tom ought not to me your secret, but he meant no harm.
A. have told B. tell
C. be telling C. having told
21. Everyone is here. we start the meeting?
A. Can B. Must C. Should D. Shall
22. I parked my car right here but now it's gone. It .
A. must be stolen B. may be stolen
C. must have stolen D. must have been stolen
23. He the work yesterday, but he didn't.
A. must have finished B. need have finished
C. finished D. should have finished
24. He did not pass the examination. As a good student, he .
A. mustn't have failed B. may not have failed
C. needn't have failed D. shouldn't have failed
25. it be true that Albert passed the test in geography?
A. May B. Should C. Could D. Would
26. You lead a horse to the water but you not make it drink.
A. will…can B. may…can
C. may…dare D. dare…can
27. -Must we finish the composition in class?
-No, you .
A. needn't B. mustn't
C. won't D. shouldn't
28. Her eyes were red. She .
A. must cry B. must be cried
C. must have been crying D. may cry
29. Mary his letter; otherwise she would have replied before now.
A. has received B. must receive
C. couldn't have received D. shouldn't have received
30. I told Sally how to get here, but perhaps I for her.
A. had to write it out B. must have written it out
C. should have written it out D. ought to write it out
31. As usual, he put on a show as though his trip a great success.
A. had been B. has been C. were D. was
32. Looking round the town, he felt as though he away for ages.
A. has been B. was C. is D. had been
33. John is so strongly built that he looks as if he an elephant.
A. lifts B. is lifting C. lifted D. could lift
34. He described the town as if he it himself.
A. had seen B. has seen C. saw D. sees
35. At that thought he shook himself, as though he from an evil dream.
A. woke B. wakes C. would wake D. had woke
36. Most insurance agents would rather you anything about collecting claims until they investigate the situation.
A. do B. don’t C. didn’t D. didn’t do
37. Although most adopted persons want the right to know who their natural parents are, some who have found them wish that they the experience of meeting.
A. hadn’t B. didn’t have had C. hadn’t had D. hadn’t have
38. He insisted that the sky ____ clear up the following day.
A. would B. should C.／ D. be
39. Without electronic computers, much of today’s advanced technology .
A. will not have been achieved B. have not been achieved
C. would not have been achieved D. had not been achieved
40. He told her to return the book in time so that others a chance to read it .
A. may have B. will have C. would have D. might have
41. It is time that the government measures to protect the rare birds and animals.
A. takes B. took C. has taken D. taking
42. Some people are too particular about school records, insisting that every applicant ______ all diplomas from elementary school to university.
A. has B. will have C. should have D. must have
43. He was very busy yesterday; otherwise he to the meeting.
A. would come B. came C. would have come D. had come
44. I must say he reads very well, and I shouldn’t be surprised if he acting for a living one day.
A. had taken up B. takes up C. have taken up D. would have taken up
45. If I had seen the movie, I you all about it now.
A. would tell B. will tell C. have told D. would have told
46. I hadn’t expected Henry to apologize but I had hoped .
A. him to call me up B. him calling me up
C. that he would call me up D. that he will call me
47. I had hoped that John a year in Africa, but he stayed there only for three months.
A. spends B. spent C. would spend D. will spend
48. I had hoped that Jennifer a doctor, but she wasn’t good enough at science.
A. will become B. became C. would become D. becomes
49. I’d rather you anything about it for the time being.
A. do B. didn’t do C. don’t D. didn’t
50. -Did you blame the accident on him alone ?
-Yes, but I ______so .
A. would rather not do B. shouldn’t do
C. shouldn’t have done D. better have not done
责任编辑：李芳芳