1、情态动词知识拓展一、lcan & could1.can表示推测通常用于疑问句或否定句Can the news be true?She cant be at home.2.can表示常有的行为或情形在肯定句中，表示客观常有的可能性，常用来说明人或事物的物征，译成“时常会”，“有时会”。It can be quite cold here in winter.As a human being, anyone can make a mistake.Im confident that a solution can be found.He can be very forgetful sometimes.3
2、.can表示惊异、怀疑、不相信等态度主要用在否定句、疑问句和感叹句Can this be an excuse for not giving them help?This cant be true.How can you be so crazy！4.can用于惯用句式1)“cannot too/enough”表示“无论怎么也不（过分）”,越越好”You cannot be too careful when crossing the street.过马路越小心越好。You cannot praise him too much. 你怎么表扬他都不过分。I can never thank him en
3、ough.我对他感激不尽。2)“cant help doing sth”/“cant help but do sth”/cant wait to do sth表示“不禁，忍不住，不得不（做某事）”Hearing the news, I cant help laughing.I cant help but be sorry about it.我不能不为之感到遗憾。I cannot help but admire her courage. 我情不自禁地钦佩她的勇气。3)“cannot but do sth”表示“除此 之外，别无他法，”。I couldnt but laugh on his fun
4、ny face.看到他那张滑稽的脸，我只能笑了笑。4)cannot +比较级表示“太”The weather couldnt be better.天气太好了。二、may & might1.表示猜测通常只用在肯定句或否定句中，含有“或许”“大概”“可能”之意，用might代替may时，则语气显得更加不肯定。疑问句中，表示可能性用can。It may rain this afternoon.She might come to join us this afternoon.I suppose he might have missed the train.- I believe the man is
5、from England. - But I may be wrong.The guest may arrive this afternoon.Where can he be?2.表示请求许可比can正式，can侧重客观情况的许可，may侧重说话人给予的许可；表示请求的疑问句回答，肯定用may或can，否定用mustnt或cant- May I come in? - Yes, you may/can. - No, you cant/mustnt.You may go now.3.表示祝愿May you succeed!May you have a good journey!4.惯用句式1)“ma
6、y as well或might (just) as well+动词原形”意为“最好，满可以，倒不如”，相当于“had better.There is nothing to do, so I may as well go to bed.You may as well tell us now, well find out sooner or later.I suppose we might as well go home.三、will & would1.表示意愿、决心用于各人称，would表示过去的意愿或决定，will表示现在或将来的I will do my best to help you.My
7、 neighbors said that they would help me to look after my dog when I went to London on a business trip.I wont be late for work this time, since the traffic is not so heavy.2.表示习惯性或规律性用于各人称，would表示过去习惯动作或倾向，意为“总是、惯于”，will表示现在Man will die.I would play basketball 10 year ago.The door wouldnt open, no ma
8、tter how hard she pushed.When we worked in the same office, we would often have coffee together.3.wont表示总是有不好的情况发生The door wont close.- Kate, whats wrong with your pen again? There isnt enough time.- The ink wont come out.四、shall & should1.shall用于一、三人称表征求意见Mr. Smith wants to see you, manager. Shall
9、he wait outside or in the office?2.shall用于二、三人称表许诺、警告、命令、威胁、必然性Dont worry, you shall get the answer this afternoon(允诺)He shall be sorry for it one day, I tell you. (警告）You shall do as I say. If you children dont do as I tell you, you shall not go to the party. (命令) (威胁)The Persons under 18 shall not
10、 be employed in night work不满十八岁的人不得雇佣干夜间工作。(表规定)That day shall come. (表必然性)3.shall表示强制用于法令、条约、规章中，意为“必须，应该”。Candidates shall remain in their seats until all the papers have been collected. 试卷完全收回后，应试人才能离开座位。4.should表示推测用在肯定句中，对现在的情况或可能发生的事的主观推测或期待，常译为“可能”，“总该吧”，“按理应当”等，相当于be expected to.should表示推断时，
11、语气较肯定，通常是指非常可能的事(因为暗示有一定的事实依据或合乎常理)Its nearly 8 oclock. My father should be home.It should be a nice day tomorrow.Its nearly 7 oclock .Jack should speak in such a way.5.should表示现在或将来的责任或义务译作“应该”，“应当”，这时可以和ought to, be supposed to互换作用You should (are supposed to) complete your test in time.You should
12、(ought to) tell your mother about it at once.6.should表示意外、惊讶的情绪用于疑问句或感叹句中，意为“竟会”，与why，what，how，who连用“Why/ How/Who+should”表示说话人对某事不能理解，如果是疑问句，则不需要回答。should可表示说话人的惊奇、愤怒、失望等感情,有时译为“竟然”。Its strange that he should come so late.Im sorry that this should have happened.Im surprised that he should say so.Why
13、 should anyone want to marry Tony?Dont ask me. How should I know?五、must & have to1.must表示猜测意思是“准是”，“一定”，一般用于肯定句中。You must be the new teacher.2.must表示“偏要”，“硬要”往往是令人不愉快的事情。If you must go, at least wait until the storm is over.Must you make so much noise?Why must he do it that way?3.must用于一般疑问句肯定回答用mus
14、t，否定式用neednt或dont have to，表示“不必”- Must I finish all assignment at a time? - Yes, you must. / No, you neednt.4.mustnt表示“禁止，不允许”mustnt只表示“不准，不应该，禁止”等意，无猜测含义It must be my mother.He must be waiting for you now.It must have rained last night ;the ground is wet.六、need & dareneed & dare可做情态动词，也可以作实义动词。用作情态
15、动词时，主要用于否定句和疑问句。1.need & dare 作情态动词- Need I come? - Yes, you must.You neednt telephone him now. 你现在不必打电话给他。I dont think you need worry. 我想你不必担心。She dare not go out alone at night. 她晚上不敢独自出去。How dare you say Im unfair? 你竟敢说我不公平？2.Need & dare 作实义动词You dont need to do it yourself.We need to tell them t
16、he news.The table needs painting. (=needs to be painted)We should dare to give our own opinion.dare用作实义动词，在否定句中，可以省略toHe didnt dare (to) look up.七、情态动词+have done（都是表示对过去的情况的推测）1.cant have done此时，can只用于否定句或疑问句，不用于肯定句。He cant have seen her there. 他不可能在那儿见到了她2.could have done某事本可以发生却没有发生，本应该做却没有做，也可指委婉
17、的批评。He could have gone home. 他可能已经回家了。He could have told her, but he didnt choose to. 他本来可以告诉她的，但他却没有。3.might have done过去可能发生却没发生，也可表委婉的批评。It was really very dangerous. I might have killed myself. 太危险了，我差点没命了。4.must have done对过去的事情进行肯定的猜测I didnt hear the phone. I must have been asleep. 我没听到电话响，一定是睡着
18、了。5.should have done本该发生却没有发生的事情The train should have already left. 火车大概已经开走了。6.shouldnt have done不应该发生却发生You shouldnt have left so soon. 你本不该那么早就走的。7.ought to have done过去本该发生却没有发生I dont think you ought to have done that. 我想你不应该这样做的。8.neednt have done过去本不必要发生的事情You neednt have come in person. 你本不必亲自
19、来的。9.would have done对过去可能发生的情况进行推测You would have heard of it.你已经听到那事了吧。10.darent have done常用于否定句中，表示做了原来不敢做的事。He didnt pass the exam. He darent have gone home.八、表猜测语气的反意疑问句的构成(做题方法：把情态动词去掉，找出谓语动词原型，按句子原来时间确定时态，写出新句子，再根据新句子写反意疑问句)例如：原句子He must be reading, _ he?新句子He is reading, isnt he?原句子He must have gone over the article, _he?新句子He have gone over the article, hasnt he?You must know the answer to the question, _ you?It must have rained last night, _ it?He couldnt go to Lilys party last Sunday, _ he?5
