1、can和could (could为can的过去式) 的基本用法

(1)表示能力，如：He can speak English better than you.

(2)在疑问句和否定句中表示“怀疑”、“猜测”或“可能性”，如：Can this green bike be Liu Dong's?

(3)表示“许可”时can可以和may换用，如：You can (may) go home now.

 (4)如果要表示语气婉转，可用could代替can，这时could不再是can的过去式，如：Could you come again tomorrow?

(5)can和be able to都可表示能力，两者在意思上没有什么区别。但是can只能有现在式和过去式，而be able to则有更多的形式，如：He will be able to do the work better.

   2、may和might (might为may的过去式)的基本用法

   (1)表示允许或征询对方许可，有“可以”之意，如：You may use my dictionary. 在回答对方说“可以做某事”或“不可以做某事”时，一般多不用may或 may not，以避免语气生硬或不容气。而用比较婉转的说法进行回答。如：---- May I use this dictionary? ---- Yes, please. 或 ---- Certainly. 在请求对方许可时，如果Might I…?就比用May I…? 语气更婉转些，如：May I have a look at your new computer? 但是表示“阻止”或“禁止”对方做某事时，要用must not代替may not，如：---- May we swim in this lake? ---- No, you mustn’t. It’s too dangerous.

(2)may或 might都可以表示可能性，表示“或许”、“可能”之意，如果用might表示可能性，则语气更加不肯定，如：They  may (might) be in the library now .

(3) may在句中表祝愿。例如：
May good luck be yours！祝你顺利。
May there never be another world war. 但愿不再有世界大战。
May you succeed! 祝你成功!

3、must的基本用法

(1)must表示“必须”、“应该”之意，其否定式 must not，缩写形式为 mustn't，表示“不应该”，“不准”、“不许可”或“禁止”之意，如：We must study hard and make progress every day. You mustn't touch the fire.

(2)对以must提出的疑问句，如作否定回答时，要用needn't或用don't (doesn't) have to (不 必)来回答，而不用mustn't，因为mustn't表示的是“禁止”或“不许可”之意，如：---- Must we finish the work tomorrow? ---- No, you needn't (don't have to), but you must finish   it in three days.

(3)在肯定句中must可以表示推测，表示“一定”或“必定”之意，如：---- Whose new bike can it be? ---- It must be Liu Dong's. I know his father has just bought him a new one.

4、can, could, may, must后接完成式的用法

(1)can, could后接完成式的用法：①在否定句或疑问句中表示对过去发生过的事情的“怀疑”或“不肯定”的态度，Could he have said so? ②在肯定句中，可以表示过去可能做到而实际并没做到的事情，有“劝告”或“责备”的语气。如：---- When did you answer her letter? ---- Only yesterday. ---- It's too late. You could have answered it earlier, I am sure.

(2)may, might后接完成式的用法 ①表示对过去某事的推测，认为某一件事情在过去可能发生了。如果使用might，语气就比较婉转或更加不肯定，如：Mary might have learned some Chinese before. ②可以表示过去本来可以做到而实 际没有做到的事情，有“劝告”或“责备”的语气，如：You didn't do the work well that day. You might have done it better.

(3)must后接完成式的用法：表示对过去某事的推测，认为某事在过去一定做到 了，如：Liu Dong isn’t in the classroom. He must have gone to the library.

5、have to 的基本用法：have to和must的意义相近，只是 must侧重表示说话人的主观看法，而have to则表示客观需要，如：I must study hard. I had to give it up because of illness.                                               

6、ought to的基本用法

(l)表示根据某种义务或必要“应当”做某事，语气比should强，例如：Everyone ought to obey the traffic regulations.

 (2)表示推测，注意与must表示推测时的区别：He must be home by now .(断定他已到家)，He ought to be home by now .(不十分肯定)，This is where the oil must be.(比较直率) ，This is where the oil ought to be. (比较含蓄)；

(3)“ought + have+ 过去分词”表示过去应做某事而 实际未做。例如：You ought to have helped him. (but you didn’t) 这时，ought与 should可以互相换用。注意，在美国英语中ought to 用于否定和疑问句时to可以省略。例如：Ought you smoke so much? You oughtn’t smoke so much.

     7、dare的基本用法

(l)dare (dared为其过去式) 作情态动词用时，主要用于否定句，疑问句和条件从句中，如：Dared he bread the traffic regulations again?

(2)在现代英语中dare常用作行为动词，其变化与一般行为动词相同，如：She dares to stay at home alone at night.

8、need的基本用法

(1)need作情态动词用时，主要用于否定句和疑问句中，如：He needn't worry about us now. 

(2)need也可作为行为动词用，可用于肯定句，否定句和疑问句中，其后可接名词、代词、动名词或带to 的动词不定式为其宾语。如：You need to practise reading aloud every day. (3)needn't后接完成式可以表示过去做了一件本来不必要做的事情，如：---- Did you answer the letter yesterday? ---- Yes, I did. ---- But you needn’t have answered it.

9、shall的基本用法

(1)shall用作情态动词时，用于第二、三人称，表示说话人的意愿，可表示“命令”、“警告”、“强制”、“威胁”或“允诺”等意，如：He shall go first, whether he wants to or not.

(2)在疑问句中，shall用于第一、三人称，表示说话人的征询对方意见或请求指示，如：Shall I open the door?

10、should的基本用法

(1)should作为情态动词可以表示“建议”或“劝告”，有“应该”之意，如：You should learn from each other.

(2)should后接完成式表示过去没有做到本来应该做的事情，或是做了本来不应该做的事情。如：You should have give him more help.

2. 竟会,竟然(与why, who, how 等连用, 表示意外、惊异等)

如:It is simply a miracle that rice should grow in such a place. 稻子竟能在这样的地方生长, 这实在是个奇迹.

 How should he know? 他怎么会知道呢?

11、will的基本用法

(1)用于各人称，可以表示“意志”或“决心”，如：I have told him again and again to stop smoking, but he will not listen.

(2)在疑问句中用于第二人称，表示说话人向对方提出请求或询问对方的意愿，如：Will you please tell me how to get to the Capital Gymnasium?

(3)will可以表示一种习惯性的动作，有“总是”或“会要”之意，如：Every morning he will have a walk along this river.

12、would的基本用法

(1)would作为will的过去式，可用于各人称，表示过去时间的“意志”或“决心”，如：He promised  he would never smoke again.                          

 (2)在疑问句中，用于第二人称，表示说话人向对方提出请求或许问对方的意愿时，比用will的气更加婉转，如：Would you like some more coffee?

 (3)在日常生活中，学用“I would like to…”表示“我想要”或“我愿意”之意，以使语气婉转，如：I would like to do Ex.2 first.

(4)would可以表示过去的习惯动作，比used to正式，并没有“现已无此习惯”的含义。如：Last year our English teacher would sometimes tell us stories in English after class. / During the vacation he would visit me every week.

 (5)表料想或猜想，如：It would be about ten when he left home./ What would she be doing there?/ I thought he would have told you about it.

13、used to, had better, would rather的用法

(1)used to表示过去的习惯动作或状态，现在已不存在，在间接引语中，其形式可不变，例如：He told us he used to play foot ball when he was young. 在疑问句、否定句、否定疑问句或强调句中，可有两种形式。

疑问句：Did you use to/ Used you to go to the same school as your brother? 否定句：I usedn’t to / didn’t use to go there. (usedn’t 也可写作usen’t)；

Did you use to play chess? Yes, I did./ Used you to get up early in the morning? Yes, I did./ used to.

否定疑问句：Usen’t you to/ Didn’t you use to be interested in the theatre? 

强调句：I certainly used to/ did use to smoke, but it was a long time ago.；

其反意疑问句或简略回答中，也有两种形式：She used to be very fat. didn’t she?/ use(d)n’t she?

 (2)had better意为“最好”，后接不带to的不定式，例如：---- We had better go now . ---- Yes, we had (we'd better/ we had better)./ Hadn’t we better stop now? (Had we better not stop now?)/ I think I’d better be going. (用于进行时态，表“最好立即”)/ You had better have done that (用于完成时态，表未完成动作) 注：had better用于同辈或小辈，对长辈不可用。

(3)would rather意为“宁愿”，表选择，后接不带to的不定式，例如：I’d rather not say anything./ Would you rather work on a farm?/ ---- Wouldn’t you rather stay here? ---- No, I would not. I’d rather go there. 由于would rather表选择，因 而后可接than，例如：I would rather work on a farm than in a factory. / I would rather watch TV than go to see the film/ I would rather lose a dozen cherry trees than that you should tell me one lie./ I’d rather you didn’t talk about this to anyone. (句中的 'd rather不是情态动词，would 在此是表愿望的实义动词)

情态动词练习

1. If they _________ to do this work, he might do it some other way.

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

2. I was told yesterday that the company _________ me to Rome next week for a business conference.

 A. should have sent    B. were going to send C. should be sending   D. should send

3. Let's take a walk, ________?         

A. will we    B. don't we    C. do we    D. shall we

4. He was a good swimmer so he _________ swim to the river bank when the boat sank.

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

5. I went to the doctor's yesterday, I had to wait for half an hour before he ________ see me.

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

6. ---- _________ this book be yours?        ---- No, it ________ not be mine. It ________ be his.

   A. Can, must, may  B. May, might, must  C. Can, may, must  D. Must, can, may

7. "We didn't see him at the lecture yesterday. "                        "He _________ it. "

    A. mustn't attend  B. can't have attended  C. would have not attended  D. needed have attended

8. They _________ the plane, or perhaps they have been prevented from coming for some reason.

   A. can have missed    B. may have missed     C. can have lost  D. may have lost

9. Since the ground is white, it _________ last night.

A. had snowed B. must have snowed C. must be snowing  D. must have been snowing

10. You must be fifty, ________?

         A. mustn't you    B. needn't you             C. aren't you      D. mustn't you

11. You must have seen him off yesterday, _________?

     A. haven't you      B. didn't you        C. mustn't you       D. needn't you

12. ---- That must be a mistake.                  ---- No .it _________ be.

     A. can't       B. isn't able to          C. can    D. was able to

13. He had known the matter before you told him, so you _________ have told it to him.

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

14. How ________ so?

     A. dare you to say     B. dare you say        C. do you dare say     D. dare to say

15. You are their teacher. You _________ care of them.

    A. should to take   B. might to take              C. ought to take        D. need to take

16. She is studying medical science now but she _________ a lawyer.

     A. used to be        B. would be        C. were      D. had been

17. If you were in an English-speaking country, you, too, _________ English every day.

     A. will be used to speak                           B. will be used to speaking

     C. must be used to speak                     D. would be used to speaking

18. I did not call to make my airline reservation (预订) but I _________.

    A. should have       B, may have         C. must have        D. shall have

19. As a girl, she _________ get up at six every day.

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

20. Don't you remember that we _________ to the cinema tonight?

    A. would go        B. go                 C. are going          D. will be gone

21. ---- 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

22. "Would you mind if I open the window?"                “__________”.

   A. I don't like it        B. Yes .please     C. No, please      D. No. I'm sorry

23. "Would you tell me something about the affair?"           

    A. Yes .please        B. All right          C. Not at all           D. I do

24. M:________?

   T:I'd love to, but I'm afraid I have no time."

   M:0h, no. You'll surely come over.

   T: It's very nice of you. But I'm sorry I have to go to a meeting.

 A. Do you have lunch out in a restaurant        B. Shall I have you with me at my birthday

    C. Did you go to see the film             D. Have you enjoyed yourself at the party

25. "You ought to have come here ten minutes ago?"                   "Yes, I _________. "

    A. ought to         B. ought to have           C. ought       D. have ought to

26. "Would you like to go out for a walk?"                     "Yes, ___________. "

   A. I'd like to       B. I'd like            C. I'll like to      D. I would

27. ________ you succeed !

     A. Can               B. May              C. Must                D. Will

28. Did he need ________ then?

 A. leave              B. to leave       C. leaving        D. left

29. Do you think if he dares _________ in public.

    A. speak         B. speaking         C. to speak        D. spoken

30. He ________ eating American food since he came here.

   A. used to     B. has been used        C. has been used to        D. was used to

31. A computer ________ think for itself; it ________ be told what to do.

    A. may not, must   B. mustn't, might      C. shouldn't, could     D. can't, must

32. "________ you mind my opening the window?"                    "Not at all. "

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

33.1 didn't hear the phone. I _________ asleep.

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

34. You _________ me about it earlier, but you didn't.

     A. should have told  B. would have told     C. must have told    D. should tell

35. The teacher told the students that they ________ keep silent in class all the time.

     A. ought to not     B. ought not to      C. ought not to have       D. can't

36. "May I go now?" "No, you ________. "

     A. mustn't             B. needn't            C. mightn't              D. won't

37. You _________ do the exercise if you don't want to.

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

38. You _________ pay more attention to your spelling next time.

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

39. The girl _________ out alone at night.

   A. dare not go     B. dare not to go         C. dares not go     D. does not dare go

40. There ________ be a lot of small houses on both sides of the street.

A. used to   B. get used to           C. would  D. did use to

 

参考答案：

1~5 ABDDD  6~10 CBBBC  11~15 BACBC  16~20 ADAAC  21~25 ACBBB

26~30 ABBCC  31~35 DDBAB  36~40 ADBAA