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1、情态动词 Modal Verbs,情态动词本身不表示动作或状态，只表示说话人认为某件事“能不能/该不该/可不可以做”等的看法。 情态动词不能单独构成谓语，必须与动词原形连用，一起构成谓语。没有人称和数的变化。,情 态 动 词 的 形 式,can (could), may (might)dare (dared), shall (should), will (would)must, need, ought toused to，had better，would rather be able to, have to,情态动词表示推测,must, may, might, can, could, 表示推测
2、must/may/ might/常在陈述句中表示可能性，must比may/ might可能性要强。 must maymight can/ could常在疑问句和否定句中表示可能性 cancould Modal verb +v. (be,动词原形）对现在行为的推测 Modal verb +have done 对过去行为的推测,表推测时must一般用于肯定句。 must的肯定程度比may/might大得多，译为“肯定” a. He must be in his office now for he called me from there five minutes ago. b. Put on mo
3、re clothes. You must feel cold with only a shirt on. c. I didnt hear the phone. I must have been asleep.,表推测时may/might 一般用于肯定句。 may表示推测的可能性比might大 a. She is coming to us. She may/might be our class teacher. b. My mother may be cooking now. c. He seems to know the city quite well. He may/might have b
4、een there before.,表推测时can/could 一般用于疑问句和否定句。 Can表示推测的可能性比could大 The young girl cant / couldnt be our new leader.Can/Could this news be true? b. He cant/couldnt be reading in the reading room, for I saw him in the street just now. c. I dont know why she didnt call me yesterday. She cant/couldnt have
5、forgotten my telephone number.,may/ might have done,可能已经做了某事,must have done,一定已经做了某事了吧,can/ could not have done,不可能做了某事,may/might not have done,可能没做某事,Modal verb +have done,You must have had a terrible dream last night. They may/might have heard the news. He may/might not have been to Beijing. 4. He
6、 cant have been working when I saw him. 5. Where can/could he have gone?,should have done/ ought to have done 本应该做，但没做 should not have done/ ought not to have done 本不应该做，但做了 could have done 本有能力做，但没做成,You should / ought to have told me the truth early.They shouldnt / oughtnt to have watched TV last
7、night. He could have finished the work but he didnt try his best.,need not have done表示过去做了没必要做的事情。 You neednt have gone to work yesterday because you were on holiday.didnt need to do 过去没必要做某事，实际也没做The teacher told him that he didnt need to hand in the composition right now, so he decided to write it
8、 after the class.,1. Joe _ (call) his sister last night, but he arrived home so late that he was not able to call her. 2. You _ (scold) him because he had tried his best. 3. -I didnt go to work yesterday because my car broke down. -You _(use) mine. I wasnt using it. 4. I was assured by the doctor th
9、at my son only had a bad cold, and nothing was serious. I _ about it.,should have called,(=ought to have done),should not have scolded,(=ought not to have done),could have used,neednt have been worried,Practice,情态动词的其他用法,may/ might:,1. 表示许可（permission）,May / Might I come in? You may / might stay her
10、e for as long as you like.,回答时，一般避免说Yes, you may或No, you may not.而常用如：Yes, please./ Please dont./ No, you mustnt., The manager said I might look around.,2. 表示祝福,May you succeed! (May you have a) good day! c.f. I wish you good luck!,3.may/ might as well:打算或建议, I may as well start at once. You may/ mi
11、ght (just) as well make a phone call to your Mum first if you want to stay here for the night.,can/ could:,1. 表示能力（ability）,He is eighty but he can still read without glasses. (ability) c.f. He was eighty then but he could ,2. 表示许可（permission）和may相近,You can go at four oclock. Can / Could I park here
12、? Yes, you can. No, you cant.,could表示过去的一般能力，was/ were able to表示过去经过努力而做成了某事的经历，相当于managed to, succeeded in,When he was young, he could read without glasses. He thought he could jump over 1.80 metres, but he was not able to. I ran fast and could catch the bus.(x)I ran fast and was able to catch the
13、bus.,could & was/ were able to,must:,1. 表示必须 (necessity),We must do everything step by step. Teachers must show concern for every student.,mustnt 不准，不许，严禁 You mustnt litter everywhere. dont have to/ neednt 没必要 Must I leave now? No, you neednt / dont have to.,must:,2. 偏偏, 偏要,When everybody was in bed
14、, he must turn his radio on. As I was sitting down to supper, the telephone must ring.,must 强调主观原因，have to强调客观原因，因环境所迫，“不得不”,John, you must be back home by ten oclock. I have to be back at school by eight. I have a lot of work to do tonight. As there is no direct transport, you have to change buses.
15、,must & have to,will:,1. 表示意愿(willingness),If you will not receive the credit card, I shall pay cash. I have told him many times but he wont listen to me. He said he would lend me some money if I asked him.,2. 表示能力，内在倾向性 The hall will seat 1,000. The door wont open.,will / would:,3. 表示请求,邀请(request)
16、,主语常为第二人称,Will you help me to put these books in order? Would you like to play cards with us? Would you mind opening the window?,will / would :,3. 表示习惯性的动作(habit),Boys will be boys. He will always bring a bunch of flowers when he comes to see me. When he was young, he would go to the cafe on the corner after work. In those days, he would work for hours at night.,
