Grammar—Modal-verb Ⅰ.情态动词 一、can/could 1.表示能力时 was/were able to 具体做成某件事（=managed to do ） could 只表示能够 2.can+感官动词 can taste/ see/ hear/ smell/ feel/ believe/ decide/ understand 3.can表示惊讶、不敢相信 Eg: How can you do like this? 4.cannot but do cannot choose but do cannot help but do Eg: I cannot but feel sorry for her. I cannot choose but follow her advice. 5.cannot… over/ enough/ too …都不过分；越…越好 Eg: You cannot over praise him. 6.理论上的可能性： Eg: Accidents can happen on such rainy days. Anyone can make mistakes. The temperature can fall to -40℃. 7.can’t 表示否定推测： Eg: It can’t be him, for he has gone to Paris yesterday.不能用mustn’t 8.can/could 表示允许、请求 Can/May I help you? I wonder if I can/could do sth.(此处could不表示时态) -Can/Could/May I use…? -Yes, you can/may. -No, you can’t/ may not/ mustn’t.(题目选项中如果表否定允许有mustn’t就选mustn’t) You’d better not.(may问一般不用may回答) I’d rather you didn’t. 9.can/could (not) have done (1)本能做、没能够 (2)过去可能会做、过去不可能做 Eg: He could have killed Harry Potter, but he didn’t.（过去本能够） He couldn’t have killed him 17 years ago, and he cannot do it now, either.（过去没能够） Can he have gone to his aunt’s ?(过去可能会做) He cannot have forgotten it. （过去不可能） 二、may/might 1.may /might 推测性用法 可能 He may be right. He may not come today (可能不) He may /might come tomorrow. 注意：只用于肯定和否定句中,不用于疑问句中 2.may not 可能不 can not不可能 He may not come He can’t come 3.may as well最好 may well理应，有足够的理由 You may（might）as well stay where you are. -Shall we walk? -We may as well. 4.表祝愿 May you be happy! 5.may (might) + have +done 表示对过去发生行为的推测，也许或许已经做 It may have been true. He might not have settled the question. He may not have finished the work. I think he may have gone to bed. 6.may表示目的 Eg: You must go to bed early so that you can/may catch the train. 7.表示让步 Eg: However hard he may try, he cannot get the first place. 三、must 1. 表示义务意为“必须”（主观意志） Eg: We must do everything step by step. You mustn’t talk to her like that. -Must we hand in our exercise—books now? -No, you needn’t. / No, you don’t have to. 2.肯定推测（绝对不能用于否定推测！！！！否定推测用can’t/couldn’t） Eg: He must be ill. He looks so pale. She’s wearing a diamond necklace. She must have a lot of money. 3.偏要做，偏偏 Eg: Why must rain on Friday? Must you speak so loudly? If you must smoke, please go out! 4.must have done想必准时一定做了某事，否定是can’t/couldn’t have done 5. didn’t need to have done 过去没有必要做，具体是否做不强调 needn’t have done 本不必却做了 四、shall 1.在肯定句、否定句中表示命令、警告、威胁、许诺以及法律、规定、规章制度 Eg: You shall leave the room at once, and he shall, too. It has been announced that candidates shall remain in their seat until all the papers have been collected. -when can I get my computer back? -Well, you shall have it on Saturday. He shall be punished if he breaks the rule. You should return the book to the library tomorrow. You shall do as I say. 按我说的做。（命令） You shall have my answer tomorrow. 你明天可以得到我的答复。（允诺） He shall be sorry for it one day, I tell you. 有一天他会后悔的，我告诉你。（警告） Nothing shall stop us from carrying out the plan. 什么也不能阻止我们执行这项计划。（决心） 2.表示请求、允许 Shall he/ she/ they/ I/ we……？ Eg: Shall I open the window? Shall the driver wait outside? 五、should 1.用于第一人称疑问句中询问对方的意愿，但语气较委婉温和 What should we do now? 2.表示应该、必须，常与must 换用。（不常见） We should (must) master a foreign language at least. 3.“should+be+表语”的结构，表示推测或惊奇。 They should be back by now. I am sorry that she should be so careless. 4.“should+have+过去分词”的结构，表示过去该做而实际上尚未做的动作或行为；其否定则表示发生了不应该发生的行为。其同义结构“ought to have +过去分词”,表示过去“早应该”、“本当”之意，语气较强。 I should have thought of that. 这一点我是应当想到的。（但没想到） They should not have left so soon.他们不应当走得这么早。（但已走了） 5. 在“It is natural (strange, natural, necessary, surprised, impossible, important ) that……”句型中，主语从句中的谓语动词要用“should +do”表示理所当然”、“奇怪”、“必要”、“惊异”等的意思。在lest（以免）、for fear (that) (以防)、in case（以备万一）等之后也要用should do;在advise, suggest, order, demand, request 等的从句中同样should do It is necessary that he(should) be sent there at once. It is strange that he should say so. Let us go at once lest we should be late for the train. 6. Why/How should 结构表示说话人对某事不能理解，感到意外惊异等意思，意为“竟会” Eg: Why should you be so late today？ How should I know? 我怎么会知道？（意为：我不知道） 六、will/would 1.表示意志，决心或愿望。 Surely we will support all the people in the world in their struggle for peace. 我们一定要支持全世界人民争取和平的斗争。 He would not let me try it . 他不肯让我去试。 I will do anything for you. 我愿为你做任何事。 None is so blind as those who won’t see. 不愿看的人眼最瞎。 If you will read the book, I’ll lend it to you. 如果你愿意读这本书，我会把它借给你 2.will表示经常性、习惯性、倾向性，would表示过去的习惯行为。 He would come to see me when he was in Beijing.他在北京时，常来看望我。 Every time she was in trouble, she would go to him for help. Fish will die out of water. 鱼离开水就不能活。 3.用于第二人称作主语的疑问句中，表示对对方的请求，would的语气比will委碗 Would/will you kindly tell me the way to the station? 请问到火车站怎么走？Would you like another glass of beer? 再来杯啤酒好吗？ Would you mind cleaning the window? 请把窗户擦一下好吗？ Will you close the window? It’s a bit cold. 请你把窗户关上好吗？有点冷。 Won’t you drink some more coffee? 再来一点咖啡好吗？ 4.表可能性 This will be the book you are looking for.这可能就是你要找的书。 She would be about 60 when she died.他死时大概60岁。 5.won’t拟人化 Eg: The door won’t open. The car won’t start. 七、need 情态动词need 实意动词need 现 在 时 You need (not) do He need (not) do You (don’t) need to do He needs (doesn’t need) to do 过 去 时 You needed (didn’t need) to do He needed (didn’t need) to do 将 来 时 You need (not) do He need (not) do You will (not) need to do He will (not) need to do 八、dare 句型 时态 情态动词dare 实义动词 dare 肯 定 句 现在时 dare to dare/dares to do 过去时 dare to dared to do 否 定 句 现在时 daren’t/dare not do do/does not dare (to) do 过去时 dared not do did not dare (to) do 疑 问 句 现在时 Dare he do? Do you/Does he dear (to) do? 过去时 Dared he do? Did he dare (to) do 九、宁愿做某事 would rather do would rather do than do would do rather than do would rather sb. did prefer to do prefer to do rather than do prefer doing to doing Ⅱ.情态动词表推测 一、情态动词表推测的三种句式 1.在肯定句中一般用must (一定)，may（可能），might / could（也许，或许）。 （1）He must/may/might know the answer to this question? 他一定/可能/也许知道这个问题的答案。 （2）It is cold in the room. They must have turned off the heating. 屋里很冷，他们肯定把暖气关了。 2.否定句中用can’t / couldn’t(不可能), may not/might not(可能不)。 （1）It can’t/couldn’t be the headmaster. He has gone to America. 这不可能是校长，他去美国了。 （2）He may not/might not know the scientist. 他也许不认识那位科学家。 3.疑问句中用can/could (能……?)。 （1）Could he have finished the task? 他可能把任务完成了吗？ （2）Can he be at home now? 他现在能在家吗？ 注：以上三种句式中情态