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1、情态动词,情态动词,表示推测,不表示推测,can could may might shall should must will would ought to,have to dare (darent) need (neednt) used to,情态动词有一定的意义，但没有人称和数的变化，不能独立使用，它和后面的动词构成谓语 只作情态动词的 can/could, may/might, ought to， must 可情态可实义的 need, dare/dared 可情态可助动词的 shall/should, will/would 相当于情态动词的 have to, used to,must ,
2、 can/could, may/might 的用法,must,1.must 表示推测时， 只能用于肯定句。,e.g.这个电脑肯定出了问题。,There must be something wrong with the computer.,你努力学了一整天， 一定累了吧,You have worked hard all day. You must be tired.,must , can/could, may/might 的用法,注意：must用于肯定句中可表示“偏偏”。 Naturally, after I told her what to do, my daughter must go an
3、d do the opposite. 自然地，在我交代女儿做什么之后，她偏偏要做相反的事情.,2.must +be doing/do 表示对现在的动作进行肯定推测,e.g.他现在一定在看小说.,He must be reading novels now.,他们买了一辆新车。 他们一定很有钱.,They have bought a new car. They must have a lot of money.,3.must +have done 表示对过去发生的事情作出的肯定判断,e.g.他们在玩篮球， 他们一定完成了作业。,They are playing basketball, they m
4、ust have finished their homework.,路是湿的。昨天晚上一定下雨了。,The road is wet. It must have rained last night.,对现在或将来情况推测：must +动词原形。 must只能用于肯定。否定和疑问分别用cant和can。 e.g. He must tell a lie. Can he tell a lie ? He cant tell a lie. *must-should/ought to may-might/could+do 可能性依次减弱,(对过去情况推测：must may, might)+完成时。 e.g.
5、 You must have met him before. mustmaymight可能性依次减弱 must只能用于肯定句，译成“一定”。否定和疑问分别用cant / couldnt和can / could。 e.g. Could /Can it have happened last night ? It couldnt/cant have happened last night.,He must be reading, isnt he? You must do it yourself, dont you? He must have gone over the article, hasnt
6、he? It must have rained last night, didnt it?,表猜测语气的反意疑问句的构成,can, could 和be able to的用法,e.g. She can/be able to sing the song in English. This machine can make you feel comfortable.,1.can, be able to都可表示“能力”,can的主语是人或物,be able to的主语是人,can, could 和be able to的用法,e.g. Well be able to finish the work soo
7、n. I havent been able to see the film.,2.can只用于现在时和过去时(could)。be able to可以用于各种时态。,could用于表示泛指过去的能力。 e.g. I could read when I was four.,Although the soldier was badly wounded, he was able to tell what had happened.,3.表示特定的某一过去能力或表示成功地做了某事时，只能用was/were able to， 不能用could。,e.g. He was able to escape fro
8、m Europe before the war broke out. He was able to swim before he got tired.,表示过去的能力,can/could,1. can /could 表示推测时，只能用在否定句或疑问句中。,e.g. Its so late. Can Tom be reading?,Can it be Mr. Green?,这个人不可能是玛丽， 她生病了。,It cant be Mary. She has fallen ill.,她不可能在说谎。,She couldnt be telling lies.,在疑问句中 could 比can 更有礼貌
9、，在此不是can的过去式。 e.g. Can you wait a moment please? Liz, can you do me a favor? Excuse me, could you tell me the way to the station? I wonder if you could help me. (请求),2. can/could have done 对过去发生行为的可能性进行推测:,刚才我还看见他了， 所以他不可能出国的。,I saw him just now so he couldnt have gone abroad.,门是锁着的， 所以她不可能在家。,The d
10、oor was locked.,She couldnt have been at home.,3. can/could have done “本可以，本来可能已经”用于肯定句中，表示对过去发生的事情做出的判断.,e.g.你本来可以考的更好。,You could have had a better mark.,may/might,1.may/might表示推测时，只能用于陈述句，表示对现在或将来要发生的动作把握不大。,e.g.她们明天可能会到这里来。,They may come here tomorrow.,他们可能还在等我们呢。,They may be still waiting for us
11、.,2.might 可用于指过去的行为或者表示可能性更小。,e.g.他也许在做功课吧。,He might be doing his homework now.,我问他我是否可以离开。,I asked him if I might leave.,I asked him “May I leave now?”,3.might/may have done,表示对过去发生的动作进行可能性推测。,e.g.他可能去医务室了。,He may have gone to the clinic.,他可能已经从报纸上知道这个消息了。,He might have read about the news in the n
12、ewspaper.,4、may 表示许可，表示允许别人做某事， 也可征求对方的许可。 May I open the door? We may keep the book for two weeks. 5、用于祈使句，表示祝愿。 May you succeed! May you have a nice trip!,表示推测情态动词的重要用法.,肯定的推测 可能的推测 否定的推测 疑问的推测,must,对将来 对现在 对过去,情态动词,may, might,cant, couldnt,can, could,+ V. + V. + have done 常见must be + be doing,+ V
13、. + V. + have done + be doing 可以用not表示“可能不”,+V. + V. + have done + be doing,+ V. + V. + have done + be doing,Will /Would you do? (表请求would 更委婉)表意志，愿望，决心 would表过去反复发生的动作或某种倾向 “总是,总要” used to表过去常常（现在已没有这种习惯） “过去常常” used to 可于状态动词连用 would不可以 e.g. He used to be a quiet boy. ( ) He would be a quiet boy.
14、( ),will/would,shall/should,1.shall 用于第二、三人称陈述句中，表示说话人给对方的命令，警告，允诺或威胁。 e.g.1)You shall go with me.(命令) 2)You shall have the book when I finish it.(允诺) 3)He shall be punished.(威胁) 2. shall用于第一、三人称疑问句中，表示说话人征求对方的意见和向对方请示。 e.g.4)Shall we begin our class?（征求意见） 5)When shall Mike be able to leave hospita
15、l?(请示),3.用于条约，规定，规章等文件中，表示一种义务，多用于第三人称中。 6) “The interest _be divided into five parts, according to the agreement made by both sides.” declared the judge. A. may B. should C. must D. shall,用于表达合理推断。 e.g. It is three oclock, the football game should begin now. Mary took dancing lessons for years, she
16、 should be an excellent dancer.,2. should 的用法,2. should 的用法,注意：should可表示“居然，竟然”。 e.g.我不敢相信这样一个绅士居然对老人如此无礼。 I cant believe such a gentleman should be so rude to the old.,e.g. Young people should learn how to use computers. Every citizen ought to obey law. You ought not to go.,3. should常表示劝告、建议、命令，与ought to意义相近，但ought
