情态动词及其用法.doc

复习情态动词的用法.情态动词的基本用法1 Can /could1） 表能力，有“能”“会”“能够”的意思Can you drive a car ? -yes ,I can No, I cant 2) 表征求许可，意为“可以.?”Can I use your bike ? 我可以? (=may, 但没有may正式)注：(过去式could比can更加委婉)3)表可能性，常用于否定句，疑问句Can it be true ?Today is Sunday. He cant be at school. n Cannot (help) but do sthn Cant help doing 2 May /might1) 表许可或征求对方的许可，有“可以”的意思You may go nowMay I use your computer ?注：过去式might 表示的语气更加委婉，客气Might I use your pen for a while ?回答以may 开头的疑问句有如下表达法：May I smoke here ?-Yes , you may. No, you cant.-Yes, please. No, you mustnt在口语中can 可以代替may 表示许可，但can较随便，may 更正式Can I use your bike ，John？May I have a look at your license please，sir ？No, youd better not. 2） 表猜测，通常只用于陈述句。You may be right.n May/might (just) as well do sth 3 Must1） 表义务，“必须”You must talk to them about their study.2) 在否定结构中，表不许，禁止You mustnt smoke here. 注意must 的回答Must I clean the dining room at once ?-Yes, you must .-No, you neednt .-No, you dont have to .3) 表坚定的建议You must come and see us as soon as you get to shanghai. 4) 表推测，暗含有很大的可能性He must be ill , isnt he? (He looks so pale .)4 Have to 表“不得不”，强调“外界压力，不得已而为之”Have to 的否定式表不需要 mustnt表不允许You dont have to go there .You mustnt go there .5. Need /Dare1）need 表示“需要，必须”，作情态动词时，仅用在否定句和疑问句中，在肯定句中一般用must , have to , ought to , should 代替You neednt worryNeed you go ?No , I neednt .Yes I must. 2）dare作情态动词时，主要用于疑问句，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 ?3) dare和need 常用作实义动词，有时态，人称和数的变化。所不同的是，作实义动词时，在肯定句中，dare后面通常接带to 的不定式，在否定句和疑问中，dare后面可接带to 或不带to的不定式。You dare to swim across this river, dont you? He does not dare (to) answer .Dont you dare (to) touch it !He needs to finish it this evening . n Need doing=need to be done 6. Will / WouldWill 1）表意愿 I will help you .2)用于第二人称征求意见Will you have some more wine ?3)用于第三人称表推测-Somebody is coming upstairs-That will be Mary. 4)表将来或现在的习惯 The old man will sit by the window for hours. Would 1) 表过去的意愿 Id like to see Mr. Smith 2） 表过去的习惯When I was a child, we would get up early and go climbing.3） 表征求意见，语气比will 委婉Would you mind my smoking here?7. Shall /Should Shall 1)用于第一，第三人称，表征求意见或建议Shall we go out for lunch ?2) 用于第二，第三人称陈述句，表示一种强烈的感情：如命令，警告，禁止，威胁，允诺等语气If you dare do that , you shall be punished .3) 表示规章，指示，预言等All shall die Should 1）表示劝告，义务，建议，命令，其同义词是ought to ; 在疑问句中，通常用should代替ought to .We should learn some English .You should go to class right away . Should I open the window ?Should 的含义较多，用法较活，现介绍三种特殊用法I should think it would be better to try it again . （我倒是认为最好再试一试）You are mistaken , I should say . (依我看你是搞错了)I should advise you not to do that . （我倒是劝你别这样做）从以上例句可以看出：情态动词should用于第一人称时可以表示说话人的一种谦逊，客气，委婉的语气Should还可以用在if引导的条件从句，表示一件事听起来可能性很小，但也不是完全没有可能，相当于“万一”的意思。 从句谓语由should加动词原形构成，主句谓语却不一定用虚拟语气Ask her to ring me up if you should see her (你万一见到她，请让她给我打个电话)If you should change your mind , please let us know . （ 万一你改变主意，请通知我们）should I (if I should ) be free tomorrow I will come . （万一我明天有时间，我就来。）此外，Why (or How)+ should 结构表示说话人对某事不能理解，感到意外，赞叹，愤怒、惊异等感情，意为“竟会”Why should you be so late today ? （你今天怎么来得这么晚？）-Where is Betty living ? （贝蒂住在哪里？）-How should I know ? （我怎么会知道呢？） I dont know why you should think that I did it . (我真的不知道你凭什么认为这件事是我干的)2) should 表示允诺It should be ready at noon .3) 表示推测或可能They should finish it by now . 情态动词表“推测”的用法1） 情态动词+动词原形 -表示对现在事情的推测2）情态动词+ have done -表示对过去状况的推测和判定具体用法如下：(1) must have done 用在肯定句中，表示对过去状况的肯定性推测，意为“过去一定已经做了某事”。 It must have rained last night, didnt it? (It rained last night.) He must have been to America, hasnt he? (He has been to America.) (2) cannot have done表示否定的推测意为“过去不可能做某事”(Sb. I is knocking at the door)Who can/ could it be?n It must be our headteacher. n No, he has gone to Beijing. It cant be him.n(3) could have done 表示“过去可能已经做了某事”或者表示“过去本来可以做某事，却没有做”。(4) couldnt have done 表示对过去或已经发生事情的否定猜测。意为“不可能”(5) may have done 用在肯定句或否定句中，表示不确定的推测，意为“过去可能，也许做了某事”。(6) might have done 可以有两层意思一是表示对过去可能可能发生事情的推测二是虚拟语气用法，表示某事过去有可能发生但实际上并没有发生(7) neednt have done 表示“过去做了本来不必做的事情”(8) should /ought to have done 用在肯定句中，表示“过去本该做某事，却没有做，”用在否定句中，表示“过去不该做某事，却做了”。 E g 1 . I -have been more than six years old when the accident happened . A. shouldnt B couldnt C mustnt D neednt 2. He -have completed his work , otherwise, he wouldnt be enjoying himself by the seaside. A .should B must C wouldnt D cant 3 .This cake is very sweet . You -a lot of sugar in it . A. should put B could have put C might put D must have put 4. -Tom is never late for work . Why is he absent today ? -Something -to him . A. must happen B should have happened C could have happened D must have happened 5. I was on the highway when this car went past followed by a police car. They -at least 150 kilometers an hour . A. should have been doing B must have been doing C. could have done D. would have done ( answer: 1-5 BBDDB ) 真题精选1. He _ unwisely, but he was at least trying to do something helpful.A. may have acted B. must have actedC. should act D. would act2. You _ Jim anything about it. It was none of his business.A. neednt have told B. neednt tellC. mustnt have told D. mustnt tell3. I went there in 1984, and that was the only occasion when I _ the journey in exactly two days.A. must take B. must have made C. was able to make D. could make 4. Loudspeakers were fixed in the hall so that everyone _ have an opportunity to hear the speech.A. ought to have B. must have D. may have D. should have5. She _