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1、Maggie. LMaggie. L.特点和基本用法特点和基本用法情态动词有四类：情态动词有四类：只做情态动词：只做情态动词：must, can (could), may (might), ought to可做情态动词又可做实义动词：可做情态动词又可做实义动词：need, dare可做情态动词又可做助动词：可做情态动词又可做助动词：shall (should), will (would)具有情态动词特征：具有情态动词特征：have (had) to, used to; had better Modal Words特点特点 无人称和数的变化无人称和数的变化, 后跟后跟动词原形动词原形,否定式否定
2、式是在其后加是在其后加 “not”。 有现在式和过去式。过去式更加客气、委婉。有现在式和过去式。过去式更加客气、委婉。时态性不强时态性不强, 可用于过去，现在或将来。可用于过去，现在或将来。情态动词属非及物动词，情态动词属非及物动词，没有被动语态没有被动语态。Modal Words1. can; could表示能力和客观可能性表示能力和客观可能性,还可表示请求和允还可表示请求和允许许can/could= is /was/will be/ has been able to1).No one can do it.=No one is able to do it.Note:1.当我们要表示当我们要表
3、示“某事已成功某事已成功”，应用应用was/were able to,而而不能用不能用“could”。2). 表示惊异、怀疑、不相信的态度。表示惊异、怀疑、不相信的态度。（主要用在否定句、疑问句或惊叹句中）（主要用在否定句、疑问句或惊叹句中） Can this be true? 3). cannot be too +adj. cannot be + adj.+ enough表示表示无论怎样无论怎样也不过分也不过分,越越越好越好 Gas is very dangerous. You cannot be too careful with it.2. may ; might(1) 表示请求、允许表示
4、请求、允许May I use your pen?用用May I . 比较正式比较正式，口气上比较客气。，口气上比较客气。 2). 用于祈使句中表示用于祈使句中表示祝愿祝愿。 May you succeed! (3) 表示推测：表示推测：may+动词原形动词原形-对现对现在情况推测，意为在情况推测，意为“也许也许”。He may be very busy now.may (might) + have + 过去分词过去分词表示对过去发生的行为的推测表示对过去发生的行为的推测 He may not have finished the work. 表猜测时不用于疑问句表猜测时不用于疑问句4)表示让步和
5、目的表示让步和目的Talk louder, so (that) all may hear.You are so careless that you may break the vast.Here lies those who fought and died, so that we might live.3. must(1) 表示必须、必要表示必须、必要You must wait here.(2) must 表示的是说话人的表示的是说话人的主观主观看法，看法，have to往往强调往往强调客观客观需要需要The play is not interesting. I really _go now.
6、I _ work when I was your age. must had to 3）表示有把握的肯定推测）表示有把握的肯定推测This cant be your pen. He must have been to Shanghai. must + have + 过去分词过去分词 （过去肯定（过去肯定） must + be doing （肯定正在（肯定正在）must + 动词原形动词原形 (肯定肯定） 肯定没肯定没：cant/ couldnt疑问句：疑问句：can 4. need-表示表示“需要需要”、“必必要要”。只用在。只用在否定句否定句或或疑问句疑问句中。中。1.He neednt p
7、ay for it.2.-Need I finish it right now? 5. shall1.在二、三人称陈述句：在二、三人称陈述句：表示说话者的意表示说话者的意图；表示图；表示“命令、警告、强制、威胁、允命令、警告、强制、威胁、允许、许诺许、许诺”。2. 在在第一、三人称疑问句第一、三人称疑问句: 表示说话人表示说话人征求对方的意见或向对方请示。征求对方的意见或向对方请示。When shall he be able to leave the hospital? You shall leave now.6.dare作情态动词时，主要用于疑问句、作情态动词时，主要用于疑问句、否定句和条件
8、从句中，一般不用在肯定句中。否定句和条件从句中，一般不用在肯定句中。 How dare you say Im unfair. He darent speak English before such a crowd, dare he? 做实义动词：做实义动词：“敢敢”肯定：肯定：dare to do sth.否定：否定：dont dare ( to) do sth.疑问：疑问：dare (to) do7.will, would1）. 表示请求、建议等，表示请求、建议等，would比比will委婉客气。委婉客气。 Would you pass me the book? 2）. 表示意志、愿望和决心
9、。表示意志、愿望和决心。 I will pass the exam.3）.表示推测表示推测will be 对目前情况的推测对目前情况的推测will (would) + have done:表示对已经表示对已经完成的动作或事态的推测。完成的动作或事态的推测。主要用于第二、三人称。主要用于第二、三人称。This will be the book you want. I thought you would have finished this by now. 4). 表料想或猜想。表料想或猜想。 It would be about ten when he left home. I thought h
10、e would have told you all about it. 情态动词的问与答情态动词的问与答Could I come to see you tomorrow?Yes, you can.No, Im afraid not.could 表示请求主要用于疑问句表示请求主要用于疑问句,不可用于肯不可用于肯定句定句, 肯定回答用肯定回答用canMay I use your pen?No, you mustnt.Yes , you may.回答回答may 问句，作否定回答多用问句，作否定回答多用must not/mustnt,表示表示“禁止禁止”、“不允许不允许”。Must we hand i
11、n our exercise books today?Yes, you mustNo, you neednt / you dont have to回答回答must问句时问句时,否定用否定用neednt/dont have to.Need you go now?-Yes,I must.-No,I neednt.在肯定句中一般用在肯定句中一般用must, have to, ought to,或或should代替代替 .情态动词情态动词+have done 结构结构must have done-表示对过去事情或已完表示对过去事情或已完成动作的肯定推测。意为成动作的肯定推测。意为“一定一定”。cant
12、 have done 不可能已经做了某事不可能已经做了某事He cant have seen the film last night, because I saw him in the office .1.You must have read the book.may have done 可能已经做了某事可能已经做了某事should have doneought to have doneI think he may have gone to bed.过去本该做而实际没有做过去本该做而实际没有做You should/ought to have come five minutes earlier.
13、can/could have done ? 用在用在疑问句疑问句中表中表示对过去发生的事情表示怀疑示对过去发生的事情表示怀疑Can he have taken the book?should not have doneought not to have doneneednt have done 过去本没必要做，反而做了过去本没必要做，反而做了could have done 过去本能做到，反而没有做过去本能做到，反而没有做You could have done it better, but you didnt try your best.过去本不该做而实过去本不该做而实际上却做了际上却做了You
14、 shouldnt have talked in class.You neednt have given him the money .Ive given him 100 dollars already.巩固练习巩固练习1.- _ I go out to play now, Mum?2.- No, you _. You should do your homework first.3.A. Must; mustnt B. Must; wouldntC. May; neednt D. May; had better not2. _ you like to have a walk with us t
15、his evening?A. Did B. Would C. Should D. Can3. You _ be careful when you cross here - the traffic lights arent working.A. could B. might C. ought toD. may 4. We were all waiting for you; you _ for the seaside by yourself without leaving a message.A. mustnt leave B. neednt leave C. shouldnt have left
16、 D. couldnt have left 5. It _ be she that told him about it; it _ be you, because only you and I know it.A. mustnt; must B. couldnt; must C. mustnt; might D. couldnt; might 6. A hardworking man _ become a great scientist, but a great scientist _ be a hardworking man.A. cant; can B. may not; can C. c
17、ant; must D. may not; must 7. You _ go right now if you want, but I think you _, because we have enough time.A. must; may not B. must; cant C. may; neednt D. may; mustnt 8. - Why do you ask me to do the difficult work? - Because you _ do such a thing and nobody else is fit for it.A. would B. can C.
18、should D. may9. You _ be tired; you have been working for so long a time, but he _ be tired; he has just begun to work.A. may not; must B. must; may notC. cant; must D. must; cant 10. Its said that there are plenty of hotels in that town. There _ be any difficulty for you to find somewhere to stay.A. wouldnt B. mustntC. shouldnt D. neednt
