情态动词辨析.doc

情态动词辨析 情态动词有can (could), may (might), must, have to, shall (should), will (would), dare (dared), need (needed), ought to等 情态动词无人称和数的变化；不能单独使用，必须与其后的动词原形构成谓语一、 can, could1) 表示能力（体力、知识、技能）Can you lift this heavy box?（体力）Mary can speak three languages.（知识）Can you skate?（技能）此时可用be able to代替Can只有一般现在时和一般过去式；而be able to则有更多的时态I’ll not be able to come this afternoon.当表示“经过努力才得以做成功某事”时应用be able to，不能用Can如：He was able to go to the party yesterday evening in spite of the heavy rain.2) 表示请求和允许。

Can I go now? ----- Yes, you can. / No, you can’t. 此时可与may互换在疑问句中还可用could, might代替，不是过去式，只是语气更委婉，不能用于肯定句和答语中 Could I come to see you tomorrow? ---- Yes, you can. ( No, I’m afraid not. )3) 表示客观可能性（客观原因形成的能力）They’ve changed the timetable, so we can go by bus instead.This hall can hold 500 people at least. 4) 表示推测（惊讶、怀疑、不相信的态度），用于疑问句、否定句和感叹句中Can this be true?This can’t be done by him.How can this be true?二、 may, might 1) 表示请求和允许might比 may语气更委婉，而不是过去式否定回答时可用can’t或mustn’t，表示“不可以，禁止”Might/ May I smoke in this room? ---- No, you mustn’t.---- May/Might I take this book out of the room?---- Yes, you can. (No, you can’t / mustn’t. )用May I...？征徇对方许可时比较正式和客气，而用Can I...？在口语中更常见。

2）用于祈使句，表示祝愿May you succeed!3) 表示推测、可能性（不用于疑问句）might不是过去式，它所表示的可能性比may小1．He may /might be very busy now.2．Your mother may /might not know the truth.三、 must, have to1) 表示必须、必要You must come in time.在回答引出的问句时，如果是否定的，不能用mustn’t（禁止，不准），而用needn’t, don’t have to（不必）.---- Must we hand in our exercise books today?---- Yes, you must.---- No, you don’t have to / you needn’t.2) must是说话人的主观看法， 而have to则强调客观需要Must只有一般现在时， have to 有更多的时态形式His play isn’t interesting, and I really must go now.I had to work when I was your age.3) 表示推测、可能性（只用于肯定的陈述句）1． You’re Tom’s good friend, so you must know what he likes best. Your mother must be waiting for you now.dare, need1) dare作情态动词用时, 常用于疑问句、否定句和条件从句中, 过去式形式为dared。

How dare you say I’m unfair?He daren’t speak English before such a crowd, dare he?If we dared not go there that day， we couldn’t get the beautiful flowers.2) need 作情态动词用时, 常用于疑问句、否定句在肯定句中一般用must, have to, ought to, should代替1．You needn’t come so early.2. ---- Need I finish the work today? ---- Yes, you must. / No, you needn’t.3) dare和 need作实义动词用时， 有人称、时态和数的变化在肯定句中，dare后面常接带to的不定式在疑问句和否定句中，dare后面可接带to或不带to的不定式而need后面只能接带to的不定式1. I dare to swim across this river.2. He doesn’t dare (to) answer.3. He needs to finish his homework today. 五、 shall, shouldshall的用法：1. shall表义务，用于第二、第三人称。

如：You shall do as you see me do. 你照我的样子办He shall be punished if he disobeys. 他若不服从就要受到处罚★在当代英语中，shall多用于正式法律文字如：The vendor shall maintain the equipment in good repair.卖方须完好地维护设备★shall有时在从句中相当于must如：It has been decided that the proposal shall not be opposed.已经决定不得反对这项提议2. shall表许诺，用于第二、第三人称，用于肯定句和否定句如：You shall have my answer tomorrow. 你明天可以得到我的答复She shall get her share. 她可以得到她的一份3. shall表征询意见，用于第一、第三人称，并用于疑问句如：Shall I get you some coffee, Miss Fleure?费勒小姐，我给您点儿咖啡好吗？What shall he do next? 他下一步干什么呢？should的用法：1. 用于第一人称疑问句，表征询意见。

如：Should I open the window? 我可以开窗户吗？2. should表义务，可用于各种句式，通常指将来如：You should do what your parents tell you. 你应该照你父母的话去做事He should do some work, but he doesn’t want to.他应该做些工作，但是他不想做也可指现在如：You shouldn’t feel so unhappy over suchtrifles.对这种小事，你不应该感到这么不高兴You shouldn’t be sitting in the sun. 你不应该坐在阳光下3. should表推测，暗含很大的可能如：It’s 4:30. They should be in New York by now.现在是四点半，他们应该到达纽约了Three weeks should suffice. 三个星期应该足够了4. should可在某些从句中，表虚拟语气如：I suggest that you should stay here as if nothing had happened.我建议你应该待在这儿，好像什么事也没有发生。

She was terrified lest they should go on talking about her.她感到害怕，唯恐他们再说她的事If he should drop in, give him my message.他若来访，就将我的消息给他5. should表感情色彩，常用在以why, how开头的疑问句中如：Why shouldn’t you invite him? 为什么你不邀请他？I don’t see why we shouldn’t make friends.我不明白为什么我们竟不能成为朋友How should I know? 我怎么知道？★在that引导的从句中，should也可表惋惜、忧虑、欢乐、惊讶等感情色彩如：I’m sorry that you should think so badly of me.你竟把我想得这样坏，我感到遗憾It is absurd that such things should happen to a family like theirs.真可笑，这种事竟发生在他们那样的家庭中★should还用于一些特殊结构，表感情色彩如：That it should come to this! 事情竟到了这种地步！To think that it should have happened to me! 谁想到这种事竟发生在我身上！(2012重庆卷24) “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 【答案及解析】 D 由declared the judge可知，前面的话是法官的判词，必须强制执行。

shall用于第二、第三人称时，表义务、强制，而其它三个选项无此义2012北京春季卷21) --The room is so dirty．________we clean it? --0f course． A．Will B．Shall C．Would D．Do 【答案及解析】B shall用于一般疑问句中，主语常用第一、第三人称，表示征求对方意见或请求允许；而will和would在疑问句中，主语常用第二人称译文：--房间如此脏乱我们打扫一下好吗?--当然可以2012上海卷27) It has been announced that candidates ________re。