can’t/can not


be able to




may not/must not

might not






have to

ought to




shall not/shan’t





will not/won’t










dare not





Some of us can use the computer nowbut we couldn't three years ago. 我们当中有些人现在会使用电脑,但三年前不会。(能力)

You can go now. 你现在可以走了。(许可)

He said I could borrow his bike. 他说我可以借他的自行车。(许可)

At that timeI thought the story could not be true. 当时,我以为故事不可能是真的。(可能)

What on earth can this mean?这究竟是怎么回事?(惊异)


Could you wait a few days for the money?你能不能再等几天给你付钱?

Could you be here at eight o'clock tomorrow morning?明天早晨八点钟你能不能到达这里?

3can(主观)和be able to(客观)都可以表示能力,意思上区别不大,但can只有现在式和过去式(could),而be able to则有更多的形式。如:

No one is able to do it. (No one can do it. ) 没人做得了这件事。

We shall be able to finish the work next week. 我们下个星期完成得了这工作。

I haven't been able to find the book. 我没能找到书。

〖注〗在肯定句中,could不用来表示特定的某一过去能力,表示特定的某一过去能力要用was (were) able to。另外,was(were) able to含有“经过努力做到”的意思,而在否定句中,could不受这一限制。比较:

He could swimbut he didn’t jump into the water to save the girl. 他会游泳,但他没有跳下水救那个女孩。

He was able to swim half way before he collapsed. 他游到中途就支持不住了。


1)表示允许或征询对方许可,有“可以”的意思。用作此意时,它的否定形式可用may not,但在表示“不可以”、“禁止”、“阻止”等意思时,常用must notmustn't)代替may not。如:

You may go now. 你可以走了。

He said that I might borrow his bike. 他说我可能借用他的自行车。

May I watch TV after supper? ——晚饭后我可以看电视吗?

Yesyou may. ——可以。(不行。/不可以。)

Noyou mustn't. Noyou may not. Noyou'd better not.

〖注〗在请求对方许可时,可用Might I. . . ?代替May I. . . ?表示更礼貌一些:

Might I use your telephone?我可以用一下你的电话吗?


He may be right. 他有可能是正确的。

I hear there may be a few copies left. 我听说可能剩有几本。

He may come today(tomorrow). 他可能今天(明天)来。

He might come today(tomorrow). 他可能今天(明天)来。

She might have some fever. 她可能有点发烧。


3musthave toought to的基本用法:

1must 表示“必须”、“应该”。否定式must notmustn't)表示“不应该”、“不许可”、“不准”、“禁止”等。如:

Everybody must obey the rules. 人人都应当遵守纪律。

The work must be finished as soon as possible. 这件工作必须尽快完成。

You mustn't lend it to others. 你不应该把它借给别人。

You mustn't speak like that to your mother. 你不应该那个样子对你妈妈讲话。

2)在回答带有“must”的问句时,否定式常用need not(needn’t)don’t have to,表示“不必”,而不用must not,因为must not表示“不可以”。如:

Must I be home before eight o'clock? ——我必须在八点钟以前回来吗?

Yesyou must. (—Noyou needn't. 或—Noyou don't have to. )——是的。(——不必。)

3have to表示“必须”,“不得不”,在这个意义上与must很接近,但must表示的是说话人的主观看法,而have to表示的却是客观需要。have tomust 有更多的时态形式。如:

I must go now. 我得走了。(主观看法)

I have to go now. (客观需要)我得走了。

You don't have to worry about that. 你不必为那事担心。

He had to spend his childhood in hard workhelping his father on their small farm. 他的童年时代是在做苦活中度过的,在农场帮助他的父亲干活。

The students of today will have to know how to use the computers of tomorrow. 今天的学生应当懂得怎样使用明天的计算机。

A poor boy like me couldn't go to school in those days. That's why I already had to work when I was your age. 在那个时代象我这样的穷孩子是上不了学校的。这就是我在你们这个年龄时就已不得不做工的原因。

4ought to表示应该做的事情(和should差不多,只是口气稍重一些)或非常可能的事。如:

You ought to follow your father's advice. 你应当听从你父亲的劝告。

The emperor thought that he ought to have nothing to fear for himself. 皇帝认为他本人没有什么可怕的。

Ought he to go? ——他有必要去吗?

YesI think he ought (to). ——是的,我认为他有必要去。



He needn't pay for it. 他没必要付钱。

Need you go now? ——你有必要现在就走吗?

YesI must. NoI needn't. )——是的,我必须走了(我不必现在就走)。


How dare you say I'm unfair?你怎么敢说我不公平?

She dare not do so. 她不敢那样做。


We need to think it over. 我们需要仔细考虑一下。

Does he need to know it?他需要知道这事吗?

She didn't need to go. 她没必要去。

Who dares to go?谁敢去?

I don't dare to ask her. 我不敢去问她。



You shall do as I say. 你应当照我说的办。

Tell him that he shall have the book tomorrow. 告诉他他明天就会得到那本书的。

I promise that you shall et the book tomorrow.我保证你明天就可以拿到那本书。

Don't worry. You shall see them again before long.别着急,不久你就会见到他们。

Everything shall be done to save the ship.必须尽全力来营救这艘船。

The new regulation shall take effect on June 1st.新章程6月1日起施行。

As a man sows, so he shall reap.善有善报,恶有恶报。


Where shall I wait for you?我该在哪儿等你?

Shall he come at once?要不要他马上来?

Shall we start the meeting now?我们现在开会好吗?


You should keep your promise. 你应当遵守诺言。

We should be strict in all our work. 我们应当对所有工作严格要求。

Young people should learn how to use computers. 年青人应当学会如何使用计算机。

6will would的基本用法:


I will tell you all about it. 我会将一切告诉你的。

We'll help him if he asks us (to). 如果他提出要求,我们会帮助他的。

He won't go. 他不想去。


I'm going down to the shop after school. Will you go with me?放学后我要去商店。你愿意一起去吗?

Will you please give him a message when you see him?你见到他时能否给他带个口信?

Won't you sit down?难道你不想坐下来?


Fish will die out of water. 鱼不在水中就会死亡。

He'll talk for hours if you give him the chance. 你一给他机会,他就会讲上几个小时。


They said that they would help us. 他们说他们会帮助我们的。

I promised that I would do my best. 我答应我会尽力的。


Would you like some more bananas?你要不要再来一些香蕉?

I'd like to see your ten-speed bicycles. 我很想看看你的十速自行车。

Would you like to see a film? ——想不想看电影?

YesI'd like to. Thanks. I'm afraid I won't be able to. )——很想看。(谢谢,恐怕看不了。)


She would sit like that for hours. 她会象那样一坐就是几个小时。

Every day she would get up at six o'clock and light the fire. 每天她会在六点钟起来生火。

〖注〗注意区别used towould主要用来叙述过去某阶段所存在的习惯,而used to则暗示与现在不一样。如:

He used to get up at six. (But now he gets up at 6:30. )他过去常常六点起床。(但现在是六点半起床。)

四、虚拟猜测与推断用法:表示“可能”意义的maymightcancould的把握程度为约50%(程度大小依次为:canmaycouldmight),属于猜测,与wouldshouldneedought to等情态动词一样常以虚拟语气形式出现;must(准是、一定是)和can’t(不可能)的把握程度几乎为100%,属于推断,常有它们固定的结构。


I should have thought of that. 这一点我是应当想到的。

They shouldn't have left so soon. 他们不应当走得那么早。

You needn't have told them that. 这你本可不告诉他们的。

Where could he have gone?他能到那里去了呢?

We ought to have given you more help. 我们本应该给你们更多的帮助的。

You might at least have answered my letter. 你至少可以回我一封信嘛。

You may have read about it in the papers. 你可能在报上已经读到这件事了。


You must be hungry after the long walk. 走了那么远的路,你一定饿了。

The Chinese language must have the largest number of speakers. 讲汉语的人数一定最多。

Nonothis can't be true!不,不,这不可能是事实。

They must have arrived by now. 现在他们想必已经到达。

He can't have finished the work so soon. 这项工作他不可能完成得这样快。

Her father thought that she must have met a fairy. 她的父亲心想她一定是遇到了仙女。





1. I thought you ____ like something to readso I have brought you some books. 1986

       A. may       B. can        C. could     D. must

2. You ____ return the book now. You can keep it till next week if you like. 1988

A. can't     B. mustn't  C. needn't  D. may not

3. A computer ____ think for itself; it must be told what to do. 1991

A. can't     B. couldn't C. may not D. might not

4. —Could I borrow your dictionary?

 —Yesof course you ____. 1992

A. mightB. will       C. can       D. should

5. Peter ____ come with us tonightbut he isn't very sure yet. 1993

A. must     B. can       C. may      D. will

6. —Shall I tell John about it?

 —Noyou ____. I've told him already. 1994

A. needn't  B. wouldn'tC. mustn't  D. shouldn't

7. It's nearly seven o'clock. Jack ____ be here at any moment. 1995

A. must     B. need      C. should   D. can

8. Johnnyyou ____ play with the knifeyou ____ hurt yourself. 1996

A. won’t; can’t     B. mustn’t; may    C. shouldn’t; must        D. can’t; shouldn’t

9. The fire spread through the hotel very quickly but everyone ____ get out. 1997

A. had to          B. wouldC. was able to   D. could

10. —Do you think I could borrow your dictionary?

 — ____. 1997

A. Yesyou may borrow        B. Yesyou could

C. Yesgo on         D. Yeshelp yourself

11. —When can I come for the photos? I need them tomorrow afternoon.

 —They ____ be ready by 12:00. 1998

A. can        B. should    C. might     D. need

12. —Will you stay for lunch?

 —Sorry____. My brother is coming to see me. 1999

A. I mustn’tB. I can’t    C. I needn’tD. I won’t

13. —Are you coming to Jeff’s party?

—I’m not sure. I ____ go to the concert instead. 2000

A. must       B. would    C. should    D. might

14. Write to me when you get home.

____. 2001春】

A. I must    B. I should  C. I will     D. I can

15. Is John coming by train?

 —He shouldbut he ____ not. He likes driving his car. NMET2002

A. must     B. can       C. need      D. may

16. The room is so dirty. ____ we clean it?

     Of course. 【京2003春】

       A. Will        B. Shall      C. Would    D. Do

17. A left-luggage office is a place where bags ____ be left for a short timeespecially at a railway station. NMET2003

       A. should    B. can        C. must      D. will

18. Naturallyafter I told her what to domy daughter ____ go and do the opposite! NMET2003春】

       A. may       B. can        C. must      D. should


1. There was plenty of time. She ____. 1987

A. mustn't have hurried B. needn't have hurried  

C. must not hurry        D. couldn't have hurried

2. The plant is dead. I ____ it more water. 1987

A. will giveB. would have given C. must give    D. should have given

3. He ____ you more helpeven though he was very busy. 1990

A. might have given B. might give   C. may have given        D. may give

4. Tom ought not to ____ me your secretbut he meant no harm. 1993

A. have told          B. tell        C. be tellingD. having told

5. I told Sally how to get herebut perhaps I ____ for her. 1994

A. had to write it out    B. must have written it out

C. should have written it outD. ought to write it out

6. —There were already five people in the car but they managed to take me as well.

 —It ____ a comfortable journey. 1995

A. can't be B. shouldn't be   C. mustn't have been D. couldn't have been

7. Sorry I'm late. I ____ have turned off the alarm clock and gone back to sleep again. 2000春】

  A. might        B. should         C. can       D. will

8. I was really anxious about you. You ____ home without a word. 2001

A. mustn’t leave    B. needn’t leave      C. couldn’t have left D. shouldn’t have left

9. I heard they went skiing in the mountains last winter.

It____ true because there was little snow there. 【京2002

       A. may not be        B. won’t beC. couldn’t be        D. mustn’t be


1. Where is my pen? I ____ it. 1988

       A. might lose         B. would have lost        C. should have lost       D. must have lost

2. I didn't hear the phone. I ____ asleep. 1989

A. must be B. must have been        C. should be          D. should have been




1. Sorry. I’m afraid I ____ go to the concert with youfor the plan our manager told me to make ____ be finished today.

       A. won’t; should    B. shouldn’t; will    C. mustn’t; need    D. can’t; must

2. Are you free to meet nowor ____ this afternoon be better?

Either time is all right.

A. can        B. would    C. could     D. shall

3. I lived with my sister this summer and didn’t have to pay rent. So I ____ save most of my salary.

       A. could     B. would    C. was able to        D. should

4. Shut your mouth. Nothing ____ stop me once I’ve made up my mind.

       A. will        B. ought to C. must      D. shall

5. It was very kind of you to do the washing-upbut you ____.

       A. mustn’t have done it B. shouldn’t have done it

       C. mightn’t have done itD. didn’t have to

6. She is an easy-going person. It ____ easy to get her to agree.

       A. should be fairly        B. must be fairly    C. can be rather     D. would be rather

7. You____ pay your library fines. If notyou____ not be allowed to graduate.

       A. mayshould    B. shouldneed    C. mustwill        D. willcan

8. I’m feeling much better now so you ____ call the doctor.

      A. mustn’t  B. can’t     C. needn’t  D. shouldn’t

9. Would you be here to attend the English party this evening?


       A. shall       B. would    C. will        D. must

10. On Sundays when I was a childFather and I ____ get up early and go fishing.

       A. could     B. would    C. might     D. should

11. Mary didn’t turn up last timedid she?

 No. She____. We had changed our plan.

       A. shouldn’t have comeB. needn’t have to come

       C. didn’t need to come D. needn’t have come

12. You ____ this morning if you really wanted to see it yourself.

       A. ought to come   B. may have come  C. ought to have come D. could come

13. Could I use your bikeJack?

Of courseyou ____.

A. can        B. may       C. could         D. might

14. You ____ stop me.

Even if you ____ itI won’t allow you to swim across the river.

A. mustn’t; dare not do B. may; dare not do

C. can; dare to do         D. needn’t; dare do

15. Since he had already passed itthe boy ____ the examination again.

       A. needn’t take   B. didn’t need to take C. mustn’t take D. needn’t have taken

16. Why not put some flowers by the window?

We ____. The boss doesn’t like flowers.

A. couldn’tB. mustn’t         C. won’t    D. can’t

17. I asked Miss Jones if I____ close the window.

       A. shall       B. will        C. would    D. should

18. Shall I go and buy more fruit for the party?

       NoI have already bought 3 baskets. That____ be enough.

       A. can        B. ought to C. may       D. might

19. This looks like a different kind of stone. What ____ we do with it?

I don’t think it’s any of use. Just throw it away.

A. will        B. shall       C. would    D. do

20. Bring your raincoat along in case that it ____ rain this afternoon.

       A. can        B. may       C. should    D. must

21. Why is the new coat so large for me?

You ____ the wrong size.

A. must buyB. should have bought    C. might buy   D. could have bought

22. I have not found my English book yet; it fact I am not sure what I ____ with it.

       A. should have done B. must have done

       C. could have done       D. need have done

23. —How about paying a visit to Mr. Hersheyour former history teacher?

 —Good idea. I will e-mail him today so he____ know____ to expect us.

       A. shall; why         B. may; when        C. would; why   D. will; how

24. As is naturala man as old as he ____ be very forgetful.

       A. can        B. must      C. should    D. would

25. Is there a flight to London this evening?

There ____ be. I’ll phone the airport and find it out.

A. must      B. might     C. would    D. can

26. I ____ you the money. Why didn’t you ask me?

       A. could have lent   B. could lend          C. have lentD. lent

27. I wondered what you could be doing and what ____ be happening to you.

       A. might     B. must      C. should    D. had to

28. What ever happened to Tom?

He ____ lost.

A. may have got     B. must be  C. should have got  D. can’t be

29. ____ we be out of gas?

       No. I’m sure we are not out of gas.

       A. Could     B. Should          C. Might     D. Would

30. He had stood outside his room for a few minutes. He____ the key to the door.

       A. might lose         B. might have lost   C. should have lost D. has lost

31. ____ it be true that Tom was put into prison again?

       A. May      B. Should   C. CouldD. Would

32. My English-Chinese dictionary has disappeared. Who ____ have taken it?

       A. should    B. must      C. could     D. would

33. The line was busy; someone ____ the telephone.

       A. must have been using      B. must be using

       C. may be usingD. may have used

34. I can’t find Tom anywhere.

 He____ his homework upstairs.

       A. might have done B. must be doing   C. should have done D. is able to do

35. The room is in a terrible mess; it____ cleaned.

       A. can’t have been  B. couldn’t be        C. may have been   D. would be

36. The farmers lived near the high way.

 ____ very noisy.

       A. It must have been B. They must be        C. That might be   D. There must be

37. Show me your permitplease.

Ohit’s not in my pocket. It ____.

    A. might fall out     B. could fall out      C. should have fallen out D. must have fallen out

38. Look at these tracks. It ____ be a wolf.

It needn’t be. It ____ be a fox.

A. must; could   B. may; might        C. need; must        D. could; need

39. You didn’t hear me until now?

No. I must ____ soundly when you came in.

       A. have been sleeping     B. have slept   C. be sleeping        D. sleep

40. They ____ at least ten minutes ago.

       A. ought to leave    B. must have left    C. might leave        D. should leave

41. My brother met her at the Capital Cinema yesterday afternoonso she ____ your lecture.

       A. needn’t have attended      B. couldn’t have attended

       C. mustn’t have attended      D. shouldn’t have attended

42. Why does Linda know so much about Eiffel Tower?

She ____ have been thereor…

A. must      B. could     C. can        D. should

43. The man in charge knew nothing about the design and all his assistants had never done any designing work before.

 OhI’m afraid it ____ a success.

       A. mustn’t be         B. mustn’t have been C. couldn’t be D. couldn’t have been

44. Perhaps John’s not in.

 ____. Lookthe light’s on.

       A. Yeshe can be at home       B. Nohe shouldn’t go out

       C. Yeshe must be at home     D. Nohe needn’t go out

45. I heard they went skiing in the mountains last winter.

       It____ true because there was little snow there.

       A. may not be        B. won’t beC. couldn’t be        D. mustn’t be

46. They ____ at least half an hour before she arrived.

       A. ought to leave   B. must have left    C. might leave        D. should leave

47. —____ the plane have taken off on time?

 —I’m afraid not. The fog was too thick then.

       A. Would    B. Should          C. Can       D. Must

48. LookJohn’s fallen asleep.

Ohhe____ too late last night.

A. might sit up   B. should have sat up     C. could sit up   D. must have sat up

49. Well doneJack!

Thanks. But given more timeI ____ it better.

A. shouldn’t have done B. could have done

C. might not do D. could do

50. If human beings had been a bit less greedy and cruelmore birds and animals ____ dying out.

       A. ought to avoid          B. could have been avoided

       C. should have avoided D. might have avoided

51. Had he worked harderhe ____ the exams.

       A. would get through    B. could get through

       C. would have got through       D. must have got through

52. China now is a member of WTO.

It ____ years ago.

A. should be          B. should have been C. can be  D. may have been

53. You didn’t invite John to the party?

____ himtoo?

A. Should I invite   B. Should I have invited C. Must I invite D. Must I have invited

54. How could I thank you enough?

 Don’t mention it. Any other man____ that.

       A. must do B. could doC. would have done D. should have done

55. The train was ten minutes lateso I____ have run all the way from my house to the station.

       A. couldn’tB. shouldn’t          C. needn’t  D. mustn’t 

56. If the hurricane had happened during the daytime____ more deaths.

       A. it would have been   B. it would be

       C. there would be         D. there would have been

57. It’s said that there are plenty of hotels in that town. There____ be any difficulty for you to find somewhere to stay.

       A. wouldn’t          B. mustn’t C. shouldn’t          D. needn’t

58. Mary’s got mad and has been sent to the mental hospital. Did you tell her boss about that?

Yesbut I____ her husband first.

       A. should have told B. shouldn’t have told    C. must have told   D. needn’t have told

59. I told sally to fix him up with this jobbut perhaps I____ for her.

       A. had to write it out     B. must have written it out

      C. should have written it outD. ought to write it out

60. I didn’t go to my evening class yesterday because I lost my textbook.

You____ mine. I didn’t have any class then.

       A. could have borrowedB. might borrow

       C. must have borrowed D. ought to borrow

61. You ____ pay too much attention to your reading skillas it is so important.

       A. cannot          B. should    C. must      D. needn’t

62. What do you think of the project Mr Johnson asked us to do?

       Wellit is a very important task. You____ be too careful.

       A. must      B. can        C. cannot          D. mustn’t

63. Since you have come so far with your experimentyou ____ carry it through to the end.

       A. may       B. might    C. may well          D. may as well

64. Since we’re not in a hurrywe____ wait for the next bus as this one is much too crowded.

       A. might well        B. might as well     C. could well         D. should as well

65. I think Mr Johnson ____ come a little latebut he____ miss this important conference about his research subjectfor he has had such a strong wish to attend this conference for many years.

       A. can; mustn’t      B. may; mustn’t     C. must; can’t        D. may; can’t