情态动词讲解与练习

1、情态动词情态动词有 can (could), may (might), must, have to, shall (should, will (would), dare (dared), need (needed), ought to 等。 情态动词无人称和数的变化；不能单独使用，必须与其后的动 词原形构成谓语。一、 can, could1) 表示能力（体力、知识、技能）。Can you lift this heavy box?（体力）此时可用 be able to 代替。Can 只有一般现在时和一般过去式；而 be able to 则有更多时态。Ill not be able to come

2、 this afternoon.当表示“经过努力才得以做成功某事”时应用 be able to，不能用 Can。如：He was able to go to the party yesterday evening in spite of the heavy rain.2) 表示请求和允许。-Can I go now?- Yes, you can. / No, you cant.此时可与 may 互换。在疑问句中还可用 could,might 代替，不是过去式，只是语气更委 婉，不能用于肯定句和答语中。- Could I come to see you tomorrow?3) 表示客观可能性（客

3、观原因形成的能力）。Theyve changed the timetable, so we can go by bus instead. This hall can hold 500 people at least.4) 表示推测（惊讶、怀疑、不相信的态度），用亍疑问句、否定句和感叹句中。Can this be true?This cant be done by him.二、 may, might1) 表示请求和允许。might 比 may 语气更委婉，而不是过去式。否定回答时可用 cant 或 mustnt，表示“不可以，禁止”。-Might/ May I smoke in this roo

4、m?- No, you mustnt.用 May I.？征徇对方许可时比较正式和客气，而用 Can I.？在口语中更常见。2）用亍祈使句，表示祝愿。May you succeed!3) 表示推测、可能性（不用亍疑问句）。might 不是过去式，它所表示的可能性比 may 小。1He may /might be very busy now.2Your mother may /might not know the truth.三、 must, have to1) 表示必须、必要。You must come in time.在回答引出的问句时，如果是否定的，不能用 mustnt（禁止，不准），而用

5、neednt, dont have to（不必）.- Must we hand in our exercise books today?- Yes, you must.2) must 是说话人的主观看法，而 have to 则强调客观需要。Must 只有一般现在时，have to 有更多的时态形式。1 he play isnt interesting, I really must go now.2 I had to work when I was your age.3) 表示推测、可能性（只用亍肯定的陈述句）1 Youre Toms good friend, so you must know

6、what he likes best.2 Your mother must be waiting for you now.四、 dare, need1) dare 作情态动词用时, 常用亍疑问句、否定句和条件从句中, 过去式形式为 dared。1 How dare you say Im unfair?2 He darent speak English before such a crowd, dare he?3 If we dared not go there that day， we couldnt get the beautiful flowers.2) need 作情态动词用时, 常用亍

7、疑问句、否定句。在肯定句中一般用 must, have to, ought to, should 代替。1You neednt come so early.2. - Need I finish the work today?- Yes, you must. / No, you neednt.3) dare 和 need 作实义动词用时， 有人称、时态和数的变化。在肯定句中，dare 后面 常接带 to 的不定式。在疑问句和否定句中，dare 后面可接带 to 或不带 to 的不定式。而 need 后面只能接带 to 的不定式。1. I dare to swim across this rive

8、r.2. He doesnt dare (to) answer.3. He needs to finish his homework today.五、 shall, should1) shall 用亍第一人称，征求对方的意见。What shall we do this evening?2) shall 用亍第二、三人称，表示说话人给对方的命令、警告、允诺或威胁。1. You shall fail if you dont work hard.(警告)2. He shall have the book when I finish it.(允诺)3. He shall be punished.(威胁

9、)六、 will, would1) 表示请求、建议等，would 更委婉。Will / Would you pass me the ball, please?2) 表示意志、愿望和决心。1. I will never do that again.2. They asked him if he would go abroad.3) would 表示过去反复发生的动作或某种倾向。would 表示过去习惯时比 used to 正式， 且没有“现已无此习惯”的含义。1. During the vacation, he would visit me every other day.2. The woun

10、d would not heal.4) 表示估计和猜想。It would be about ten oclock when she left home.七、 should, ought to1) should, ought to 表示“应该”，ought to 表示义务或责任，比 should 语气重。1. I should help her because she is in trouble.2. You ought to take care of the baby.2) 表示劝告、建议和命令。should, ought to 可通用，但在疑问句中常用 should。1. You shoul

11、d / ought to go to class right away.2. Should I open the window?3) 表示推测should , ought to (客观推测), must(主观推测)。1.He must be home by now. (断定他已到家)2.He ought to/should be home by now.(不太肯定)3. This is where the oil must be.(直爽)4. This is where the oil ought to/should be.(含蓄)八、 情态动词+不定式完成式（have done）1) can

12、 / could + have done 在肯定句中表示“本来可以做而实际上能做某事”，是虚拟 语气；在疑问句或否定句中表示对过去行为的怀疑或不肯定, 表示推测。1. You could have done better, but you didnt try your best. （虚拟语气）2. He cant have been to that town.（推测）3. Can he have got the book?（推测）2) may / might +不定式完成式（have done） 表示对过去行为的推测。不能用亍疑问句中，没有虚拟语气的用法。Might 所表示的可能性比 may

13、小。1. He may not have finished the work .2. If we had taken the other road, we might have arrived earlier.3）must +不定式完成式（have done） 用亍肯定句中，表示对过去行为的推测。意为“一定、想必”。其疑问、否定形式用can，cant 代替。参看 1) can / could + have done 表示推测。1. You must have seen the film Titanic.2. He must have been to Shanghai.4）should +不定式

14、完成式（have done）用亍肯定句中，表示对过去行为的推测。He should have finished the work by now。表示“本应该做而实际上没有做某事”，其否定式表示某种行为本不该发生却发生了。 可以与 ought to +不定式完成式（have done）互换。1. You ought to / should have helped him. (but you didnt.)2. She shouldnt have taken away my measuring tape, for I wanted to use it.5) neednt +不定式完成式（have

15、done） 表示“本来不必做而实际上做了某事”。You neednt have watered the flowers, for it is going to rain.6) will +不定式完成式（have done） 主要用亍第二、三人称，表示对已完成的动作或事态的推测。He will have arrived by now.课后练习题1) You all those clothes! We have a washing machine to do that sort of thingA) neednt have washedB) shouldnt have washedC) must

16、not have washedD) can not have washed2) Johns score on the test is the highest in the class; he last night.A) should studyB) should have studiedC) must have studiedD) must have to study3) The room is in a terrible mess; it cleaned. (CET-4, 2019,6) A) cant have beenB) shouldnt have beenC) mustnt have

17、 beenD) wouldnt have been4) Nobody knows how people first came to these islands. They from South America on rafts.A) must have sailedB) can sailC) might have sailedD) should have sailed5) Mary was not in her bedroom yesterday afternoon. She in her classroom.A) should have beenB) must have beenC) mus

18、t beD) should be6) Bob said he was going to join our club but he didnt. He his mind.A) cant have changedB) wouldnt have changedC) must have changedD) shouldnt have changed7) You to town to see the film yesterday. It will be on TV tonight.A) neednt goB) had better not goC) should not goD) neednt have

19、 gone8) We the letter yesterday, but it didnt arrive.A) must receiveB) ought to receiveC) must have receivedD) ought to have received9) With all the work on hand, he to the cinema last night.A) mustnt goB) shouldnt have goneC) could not goD) couldnt have gone10) Eve was late for class again. She ear

20、lier.A) should get upB) must get upC) need to get upD) should have got up11) I am feeling sick. I so much chocolate.A) neednt have eatenB) couldnt have eatenC) mustnt have eatenD) shouldnt have eaten12) I didnt send out my application form last week, but I .A) hadB) would doC) should haveD) might ha

21、ve to13) Walking alone in the deserted village, He thought he_ Tom to go with him.A) might have askedB) should askedC) must have askedD) should have asked14) When I got to the cinema, the film had already started; I there earlier.A) ought to getB) ought to have gotC) must have gotD) must get15) The

22、road was muddy. It_ last night.A) must rainedB) must have rainedC) must be rainedD) could have rained16) She can speak quite fluent English. She _.A) must been in the U.S.A. for some timeB) must have been in the U.S.A. for some timeC) should have been in the U.S.A. for some timeD) May be in the U.S.

23、A. for some time17) You should bear in mind that he is not so strong as he .A) was used to beB) used to beC) was used toD) use to18)“We didnt see him at the exhibition yesterday.”“He _it.”A) mustnt visitB) cant have visitedC) should have gone to seeD) may see19) Mary my letter, otherwise she would h

24、ave replied before now.A) should have receivedB) has receivedC) Couldnt have receivedD) ought to have received20) I you a valuable present for your birthday, but I was short of money.A) would have liked to giveB) liked to giveC) have liked to giveD) would like to give21)“Where my umbrella?”“Somebody

25、 it away by mistake.”A) is, must have takenB) is, must takeC) have been, must takeD) is, takes22) What would happen if the director knew you felt that way?A) will you supposeB) you supposeC) do you supposeD) you would suppose23) Two eyes see more than one.A) canB) mayC) willD) should24) you continue

26、 in your efforts and achieve new and greater successes.A) WouldB) WillC) MayD) Should25) We ought to help each other in our work, ?A) oughtnt weB) should weC) shouldnt weD) ought to we26) Tom better than to ask Dick for help.A) shall knowB) shouldnt knowC) has knownD) should have known27) You your tooth pulled out before it rot completely.A) had better gotB) had to get betterC) had better to getD) had better get28) When we got to the cinema, the film hasnt started yet, so we .A) neednt hurryB) didnt need hurryC) neednt to hurryD) neednt have hurried29) It was really very dan