Modal Verbs 情态动词.

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1 Modal Verbs 情态动词

2 Definition 定义 Like auxiliary verbs, Modal Verbs are placed before main verbs which are always “bare infinitives”. Unlike auxiliary verbs, Modal Verbs have certain meanings. They are used to express the speaker’s attitude towards an act or a state.

3 Modal Verbs can / could may / might must should / ought to shall
will / would dare / dared need have to used to be to had better / best would rather

4 can / could a) The little girl could read before she went to primary school. b) Even expert drivers can make such mistakes. c) －Can I borrow these books from the library? －Yes, you can. / No, you can’t. ability 表示能力 possibility 表示客观可能性 request or permission 表示请求或允许 “could” expressing the attitudinal past 礼貌过去时 ＃

5 can / could can but (= can only) e.g. I can but wait.
cannot but / cannot help but / cannot choose but / cannot help doing (= must, to be forced to) can = is/are able to could ≠ was (were) able to cannot / can never… too “怎么…也不过分”、“应尽量…”、“越…越好” e.g. It cannot be too strongly emphasized that mathematics is the basis of science. can have done(否、疑问)/ couldn’t (could) have done e.g. She’s two hours late－what can/could have happened? She can’t/couldn’t have seen the letter But for your help, we couldn’t have finished the task.

6 may / might a) He told me that I might smoke here. b) He may not know the truth. c) May you always be happy! d) Write to him at once so that he may know in time. e) Ben may only be ten, but he plays the piano well. request or permission 表示请求或允许 －May/Might I sit here? －Yes, please./Certainly. No, you mustn’t./Please don’t./You’d better not. possibility 表示可能性 (否) can’t 不可能 may not 可能不 wish 表示祝愿 结构：may + 主语 + 谓语 purpose 用于目的状语从句中，表示目的 concession 用于让步状语中，表示让步

7 may / might might可以表示may的过去时，但更常用作may的替换词，表示现在和将来，区别在于may的肯定性比might更强。
e.g. You might have some fever I might go to a concert tonight. expressing the attitudinal past 礼貌过去时 e.g. Might I have a little water? may/might well & may/might as well e.g. It may/might well be true You may/might as well repeat the experiment. may/might well 表示可能性； may/might as well表示勉强，迁就，无奈的意思 might have done a) subjunctive mood 本可以做某事而实际没有做 b) possibility 推测过去实际上存在的可能性 (=may have done) c) seem 仿佛是，好像是

8 must 表“必须”，强调说话人的态度或义务 e.g. －Must we pack now? －Yes, you must No, you needn’t./You don’t have to. 表“推测” e.g. They must be hungry They can’t be hungry. 表“偏要” e.g. Why must you be so stubborn Just when we were ready for our holidays, the baby must catch measles. mustn’t (=forbid) 表示“禁止”

9 must must & have to must着重表示说话人主观上的看法，有很强的个人色彩； have to则着重表示客观上的“必须”，如其他人、法律、自然规律、政府要求的事。 e.g. I must be off now We have to pay our tax to the government. must have done 表示逻辑上的必然性，即过去肯定发生过某事 e.g. It must have rained last night, for the ground is still wet.

10 must 反义疑问句 We must do everything step by step, ___?
He looks pale. He must be ill, ___? She’s wearing a diamond ring. She must have a lot of money, ___? He behaved strangely last night. He must have heard the news yesterday, ___? You must have already finished writing the composition, ___?

11 should / ought to a) You should/ought to pay your debts. b) We needn’t hurry; the guests shouldn’t/ ought not to come for another hour. c) It’s incredible that he should have achieved so much these years. 表示义务和责任，“应该” 表推测，“该”、“理应”、“可能” 表出乎意料，“竟然”、“居然”

12 should / ought to should have done / ought to have done 1. 表对过去某个动作的推论或推测 2. 本应该做某事，却没做 e.g. It’s ten o’clock. She should have arrived in her office by now You should have washed the wound. shouldn’t have done / ought not to have done 本不应该做某事，却做了 e.g. You shouldn’t have left so early.

13 shall 用于第二、三人称肯定句中，表示说话人的意愿或承诺。 e.g. I promise that you shall have a car for your birthday. 用于第三人称，表示按条约、法令、规章等必须履行的义务,相当于must。 e.g. Gambling in any form shall be banned. 用于第一、三人称疑问句中，表示征求对方同意或向对方提出建议。 e.g. －Shall I/we take this away? －Yes, please. / No, thank you. 用于第二、三人称肯定句中，表示“命令”、“威胁”、“警告”等语气。 e.g. He shall be punished if he disobeys She shall suffer for this.

14 will / would a) She will/would sit there for hours, waiting for the postman. b) If the water is heated to 100℃, it will boil. c) If you will read the book, I shall lend it to you. d) Will you take the message to Jane? e) Jack will do such things! f) There’s a ring at the door. That will/would be the postman, I suppose. 表示规律性、习惯性的动作，“总是” 表示事物的倾向、特征、趋势。 表示意愿。 用于第二人称疑问句表示征求对方意见。 表示“坚持”、“执意”。 e.g. He wouldn’t take the money. 表示推测，“想必”、“也许”、“大概”、“可能”。

15 dare / dared dare既可以用作情态动词，也可以用作实义动词。
e.g. She dare say what she thinks She dare not say what she thinks She dares to say what she thinks She doesn’t dare to say what she thinks.

16 need need作为情态动词通常用于否定和疑问句中。
e.g. Need I type this letter? You needn’t hurry with it ×Tinna need leave at seven every morning. need作为实义动词既可用于肯定句，也可用于否定和疑问句中。 e.g. They didn’t not need to arrive so early Do you need to tell the same story every time we meet? You need to deal with the problem in a new way.

17 need need doing & need to be done e.g. The coffee is cold; it needs heating/to be heated. 作为实义动词的need后接动名词可以表示被动的意义，也可以用不定式的被动态表示被动。与之用法相同的还有require, want, deserve。 needn’t have done & didn’t need to do e.g. a) They didn’t need to arrive so early b) They needn’t have arrived so early. a)表示没有必要做某事，没有虚拟的意义。 b)表示本没有必要做某事但是却做了，带有虚拟的意义。

18 used to e.g. He used to live here in I used to write poetry when I was his age He used to play football before his marriage. (否) usedn’t to do (英) / didn’t use(d) to do (美) (反意疑问句) didn’t / usedn’t used to do / be used to doing / be used to do a) used to do表示过去的习惯性动作； b) be/get/become used to doing = be accustomed to doing 表示习惯于 c) be used to do表示被用来做……

19 be to a) You are to be back by 10 o’clock. b) He was never to see his family again. c) They are to find a solution to the problem. 表示“指示”、“命令”、“要求” 表示“可能” 表示“将来”、“计划”、“安排” was/were to do & was/were to have done 前者表示过去曾经计划要做某事，现在已经实现了；后者表示“本打算”、“本计划”、“本应当”做某事，却没有发生。 e.g. I felt nervous because I was soon to leave home for the first time We were to have met, but he didn’t show up.

20 Exercises I know it isn’t important but I can’t help ___ about it. A. but to think B. thinking C. think D. to think －You realize that you were driving at 100 mph, don’t you? －No, officer, I ___. This car can’t do more than 80. A. needn’t have been B. may not have been C. didn’t need to be D. couldn’t have been ___ prosperous and strong! A. Let your country become B. Hope your country become C. May your country become D. Your country it becoming Mary is very late. She ___. A. may miss her train B. may have missed her train C. must miss her train D. could miss her train Johnny, you ___ play with the knife; you ___ hurt yourself. A. won’t; can’t B. mustn't; may C. shouldn’t; must D. can’t; shouldn’t An ambulance was waiting in the street, somebody ___ hurt or killed. A. should have been B. should be C. must have been D. shouldn’t have been

21 Exercises －John didn’t come to see me this morning. －I ___ him last night but I was too busy. A. should telephone B. should have telephoned C. had to telephone D. ought to telephone －Elizabeth borrowed the book a month ago. －Then she should ___ it by now. A. to finish B. have finished C. finish D. had finished I’m very sorry for what has happened; the serious consequences ought to ___ out to those concerned at the very beginning. A. point B. be pointed C. have pointed D. have been pointed I promise that you ___ five dollars if you clean all the windows. A. have B. could have C. should have D. shall have Only in summer ___. A. will the ice melt B. the ice will melt C. the ice can melt D. the ice melts His parents ___ let him marry anyone whose family was poor. A. won’t B. wouldn’t C. shouldn’t D. couldn’t The snake hasn’t bitten me yet but I daren’t ___ to upset it. A. to do a thing B. do anything C. to do something D. do nothing

22 Exercises 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 －Why don’t you use the carving knife? －It needs ___. A. sharpened B. being sharpened C. sharpening D. to sharpen You ___ such a long essay, the teacher only asked for 300 words, and you have written 600. A. mustn’t have written B. needn’t have written C. didn’t have to write D. didn’t need to write －Have you been to Mexico? －No, I ___ last year, but Dad wouldn’t let me. A. was to have gone B. were to go C. was gone D. went －I think I’ll borrow this book from Frank. －___ take it without his permission. A. Better you don’t B. It’s better you shouldn’t C. You’d better not D. You’d better not to