1、专四语法第7节情态助动词教学内容专四语法专题第七节：情态助动词I. 情态助动词考点和知识要点：情态助动词概述：情态助动词有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。情态助动词知识要点：1. can / could2. may / might3. will, would4. shall5. should, ought to6. must7. need8
2、. dare9. 情态动词+不定式完成式（have done）1. can / could1) 表示请求和允许(Permission) -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?- Yes, you can. ( No, Im afraid not. )2) 表示能力（体力、知识、技能）(Ability)Can you lift this heavy box?（体
3、力）Mary can speak three languages.（知识）Can you skate?（技能）表示“能力”时可与be able to互换。Can只有一般现在时和一般过去式；而be able to则有更多的时态。Ill not be able to come this afternoon.但当表示“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.3) 表示客观可能性（客观原因形成的能力）(Possibili
4、ty)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），用于疑问句、否定句和感叹句中。Can this be true?This cant be done by him.How can this be true?2. may / might 1) 表示请求和允许(Permission)。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/
5、May I smoke in this room? - No, you mustnt. - May/Might I take this book out of the room? - Yes, you can. (No, you cant / 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）表示推测、可能性（不用于疑问句）(Possibility)。 might不是过去式，它所表示的可能性比may小。 He may /might be very busy now. Your mother may /might not know the t
6、ruth.3) 用于祈使句，表示祝愿。 May you succeed!4) may /might.as well表示“不妨，还是.的好”,也可以写作may /might as well. Since it is raining hard, you may as well stay here.3. will, would 1) 用于第二人称疑问句中，表示请求、建议等，would更委婉，不表时态。Will / Would you pass me the ball, please?2) 表示意愿（Willingness）、意图（Intention）、决心（Determination）、承诺（Pro
7、mise）等，可用于各种人称。I will never do that again.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。During the vacation, he would visit me every other day.The wound would not heal.4) 表示估计和猜想。It would be about ten oclock when she left home.4. shall 1) shall 用
8、于第一人称，征求对方的意见。What shall we do this evening?2) shall 用于第二、三人称，表示说话人给对方的命令、警告、允诺或威胁。You shall fail if you dont work hard.(警告)He shall have the book when I finish it.(允诺)He shall be punished.(威胁)5. should, ought to 1) should, ought to表示“应该”，ought to表示义务或责任，比should语气重。I should help her because she is i
9、n trouble.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。You should / ought to go to class right away.Should I open the window?3) 表示推测 should , ought to (客观推测), must(主观推测)。He must be home by now. (断定他已到家)He ought to/should be home by now.(不太肯定)This is where the o
10、il must be.(直爽)This is where the oil ought to/should be.(含蓄) Uncertain might may could can should ought to would willCertain must 6. must, have to 1) 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neednt, dont have to（不必）.- Must we hand in our exercise books today?- Yes, you must.
11、- No, you dont have to / you neednt. 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。 He play isnt interesting, I really must go now. I had to work when I was your age. 3) 表示推测、可能性（只用于肯定的陈述句） Youre Toms good friend, so you must know what he likes best. Your mother must be waiting for
12、 you now.7. dare, need 1) dare作情态动词用时, 常用于疑问句、否定句和条件从句中, 过去式形式为dared。 How dare you say Im unfair? He darent speak English before such a crowd, dare he? If we dared not go there that day， we couldnt get the beautiful flowers.2) need 作情态动词用时, 常用于疑问句、否定句。在肯定句中一般用must, have to, ought to, should代替。 You n
13、eednt come so early. - 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。 I dare to swim across this river. He doesnt dare (to) answer. He needs to finish his homework today. 8. wi
14、ll, would 1) 用于第二人称疑问句中，表示请求、建议等，would更委婉，不表时态。Will / Would you pass me the ball, please?2) 表示意愿（Willingness）、意图（Intention）、决心（Determination）、承诺（Promise）等，可用于各种人称。I will never do that again.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。During the
15、 vacation, he would visit me every other day.The wound would not heal.4) 表示估计和猜想。It would be about ten oclock when she left home. 9. 情态动词+不定式完成式（have done） 1) can / 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。You could have done better, but you didnt try your best. （虚
16、拟语气）He cant have been to that town.（推测）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。不能用于疑问句中，没有虚拟语气的用法。Might所表示的可能性比may小。He may not have finished the work .If we had taken the other road, we might have arrived earlier. 3）must +不定式完成式（have done）用于肯定句中，表示对过去行为的推测。意为“一定、想必”。
17、其疑问、否定形式用can，cant代替。参看1) can / could + have done表示推测。You must have seen the film Titanic.He must have been to Shanghai.4）should +不定式完成式（have done） 用于肯定句中，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。You ought to / should h
18、ave helped him. (but you didnt.)She shouldnt have taken away my measuring tape, for I wanted to use it.5) neednt +不定式完成式（have 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）主要用于第二、三人称，表示对已完成的动作或事态的推测。He will have arrived by now.II. 情态助动词
19、专四真题模拟题1. Among the four sentences below, Sentence_expresses the highest degree of possibility.A. It may take a long time to find a solution to the problem.B. It might take a long time to find a solution to the problem.C. It could take a long time to find a solution to the problem.D. It should take
20、a long time to find a solution to the problem.2. Which of the following italicized words does NOT indicate willingness?A. What will you do when you graduate?B. They will be home by now.C. Who will go with me?D. Why will you go there alone?3. When the sentence “Shall I drive you to the airport first?
21、” is turned into indirect speech, which of the following is most appropriate? A. He agreed to drive me to the airport first. B. B. He offered to drive me to the airport first. C. He advised me to go to the airport first. D. He suggested that I drive to the airport first.4. Which of the following sen
22、tences indicates POSSIBILITY?A. The moon cannot always be at the full.B. You cannot smoke inside the building.C. He cannot come today.D. She cannot play the piano.5. Which of the following sentences a fact? A. Mary and her son must be home by now. B. Careless reading must give poor results. C. He mu
23、st be working late at the office.DIts getting late, and I must leave now.6. Which of the following best explains the meaning of Shall we buy the tickets first”? AHe said that we were going to buy the tickets first BHe requested that we buy the tickets first CHe suggested that we buy the tickets firs
24、t DHe advised us to buy the tickets first7. Which of the following sentences expresses WILLINGNESS? ABy now she will be eating dinner BI shall never do that again CMy brother will help you with the luggage DYou shall get a promotion8. The sentence that expresses OFFER is _.A. Ill get some drinks. Wh
25、atll you have? B. Does she need to book a ticket now?C. May I know your name? D. Can you return the book next week?9. Nancys gone to work but her cars still there. She _ by bus.A. must have gone B. should have goneC. ought to have gone D. could have gone10. Arent you tired? I _ you had done enough f
26、or today.A. should have thought B. must have thoughtC. might have thought D. could have thought11. ，A. must take B. must have madeC. was able to make D. could make12. Which of the following sentences expresses probability?A. You must leave immediately.B. You must be feeling rather tired.C. You must
27、be here by eight oclock.D. You must complete the reading assignment on time.13. She _fifty or so when I first met her at the conference.A. must be B. had been C. could be D. must have been14. You _ borrow my notes provided you take care of them, I told my friend.A. could B. should C. must D. can15.
28、I am surprised_ this city is a dull place to live in.A. that you should think B. by what you are thinkingC. that you would think D. with what you were thinking16. Loud speakers were fixed in the hall so that everyone_ an opportunity to hear the speech.A. ought to have B. must have C. may have D. sho
29、uld have17. You _ anything about it. It was none of his business.a. neednt have told b. neednt tell c. mustnt have told d. mustnt tell 18. He _unwisely, but he was at least trying to do something helpful.a. may have acted b. must have acted c. should act d. would act 19. The meetings been canceled.
30、Ann _ all that work.a. need to do b. need have c. neednt have done d. needed not to do20. “She must be in the dormitory now.” “No, she _ be there. I saw her in the classroom a minute ago.”a. mustnt b. cant c. couldnt d. wouldnt 21. He _ the 8:20 bus because he didnt leave home till 8:25.a. couldnt have caught b. ought to have ca
