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。Ill 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 cant. 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, Im afraid not. )3) 表示客观可能性（客观原因形成的能力）。Theyve 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 cant 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cant或mustnt，表示“不可以，禁止”。-Might/ May I smoke in this room? - No, you mustnt.- May/Might I take this book out of the room?- Yes, you can. (No, you cant / mustnt. )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。1He may /might be very busy now.2Your 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mustnt（禁止，不准），而用neednt, dont have to（不必）.- Must we hand in our exercise books today?- Yes, you must.- No, you dont have to / you neednt.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 isnt 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 Youre Toms 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 Im unfair?He darent speak English before such a crowd, dare he?If we dared not go there that day， we couldnt 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。1You neednt come so early.2. - Need I finish the work today? - Yes, you must. / No, you neednt.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 doesnt 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 doesnt want to.他应该做些工作，但是他不想做。也可指现在。如：You shouldnt feel so unhappy over suchtrifles.对这种小事，你不应该感到这么不高兴。You shouldnt 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：Its 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 shouldnt you invite him? 为什么你不邀请他？I dont see why we shouldnt 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：Im 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 Amay Bshould Cmust Dshall 【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 AWill BShall CWould DDo 【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 _remain in their seats until all the papers have been collected A. can Bwill Cmay Dshall 【答案及解析】D shall用于陈述句的第二、第三人称时，表示说话人的意图、允诺、警告、命令、决心等，意思是“必须，应，可”。译文：据宣布，考生在收卷前必须坐在自己的座位上。(2012全国卷33) I was really anxious about you. You _ home without a word. A. mustnt leave B. shouldnt have left C. couldnt have left D. neednt leave 【答案及解析】B 表示原本不应该做某事，含责备之意。If I _ meet Alan or his sister, Ill tell them about the terrible accident. A: will B: can C: shall D: should 【答案及解析】D 这里表示假设万一的意思，译文：万一我遇到Alan或他姐姐，我就告诉他们这可怕的事故六、 will, would1) 表示请求、建议等，would更委婉。Will / Would you pass me the ball, please?2) 表示意志、愿望和决心。1. I will never do that again.2. They asked him if he would go abroad. 3) would表示过去反复发生的动作或某种倾向。would表示过去习惯时比used to正式，且没有“现已无此习惯”的含义。1. During the vacation, he would visit me every other day.2. The wound would not heal.4) 表示估计和猜想。 It would be about ten oclock when she left home.七、 should, ought to1) should, ought to表示“应该”，ought to表示义务或责任，比should语气重。1. I should help her because she is in trouble.2. You ought to take care of the baby.2) 表示劝告、建议和命令。should, ought to可通用，但在疑问句中常用should。1. You should / ought to go to class right away.2. Should I open the window?3) 表示推测should , ought to (客观推测), must(主观推测)。1.He must be home by now. (断定他已到家)2.He ought to/should be home by now.(不太肯定)3. This is where the oil must be.(直爽)4. This is where the oil ought to/should be.(含蓄)情态动词+have+done是历年高考的重点和难点之一，现将其用法总结归纳如下：一、 “must+have+done”表示对过去事情的肯定推测，译成“一定做过某事”，该结构只用于肯定句。 1. It must have rained last night, for the ground is wet. 昨晚一定下雨了，因为地面还是湿的。2. You must have been mad to speak to the servant. 你和仆人说话，一定是发疯了。二、 “cant+have+done”表示对过去事情的否定推测，译成“不可能做过某事”。1. Mr. Smith cant have gone to Beijing, for I saw him in the library just now. 史密斯先生不可能去北京了，我刚才还在图书馆见过他。2. Mary cant have stolen your money. She has gone home. 玛丽不可能偷你的钱，她回家去了。三、 “can+have+done”表示对过去行为的怀疑，用于疑问句，译成“可能做过吗？”。1. There is no light in the room. Can they have gone out? 屋里没有灯，他们可能出去了吗？2. There is nowhere to find them. Where can they have gone? 到处找不到他们，他们可能到什么地方去呢？四、 “could+have+done”是虚拟语气，表示对过去事情的假设，意思是本来能够做某事而没有做。He could have passed the exam, but he was too careless. 本来他能够通过考试，但是他太粗心。五、 “may+have+done”表示对发生过的事情的推测，意思是“可能已经”或“也许已经”，用于肯定句中。 What has happened to George?I dont know. He may have got lost.乔治发生了什么事？我不知道，他可能迷路了。六、 “might+have+done”表示对过去事情的推测，might与may意思相同，但可能性更小。多用于虚拟语气结构中。 1. He might have given you more help, even though he was busy. (MET90) 他或许会多给你一些帮助，即使他很忙。2. She might have achieved greater progress, if you had given her more chances. 如果你多给她点机会，她可能已经取得更大的成绩。七、 “would+have+done”虚拟语气，表示对过去事情的假设，意思是“本来会做”。1. I would have told you all about the boys story, but you didnt ask me. 我本来会告诉你