情态动词知识梳理3notes.doc

【情态动词知识梳理3】1. Can 和 may 的区别情态动词can和may都能表示“可能性”。如：He may be right. 他可能对。He cant be right. 他不可能对。那么，在表示可能性这个概念时，二者的区别是什么呢？ 二者所适用的句子类型不同。一般说来，can多用于疑问句和否定句，表示怀疑或不相信等态度；而may则多用于陈述句（肯定），表示一种揣测。如：Can it be true? No, it can not be true.Where can they be now? 二者所强调的意思不同。一般来说，can强调客观上的可能性，而may则强调主观上的推测或判断。如： Man cannot live without air or water. She may be in the library, I suppose. 二者表示的语气不同。在否定句中，can表达的否定语气较强，意为“不可能”；而may表达的否定语气较弱，意为“可能不”或“也许不”。如： That cannot be true. (=It is impossible that that is true.) That may not be true. (=It is possible that that is not true.)根据以上分析，我们可以归纳为三条原则：(1) 在肯定句中用may不用can;(2) 在疑问句中用can不用may;(3) 在否定句中，若语气肯定，表示“不可能”时用cannot，若语气不肯定，表示“可能不”时用may not.2. Can 和 be able to 的区别 can 和be able to 都可以表示能力.can泛指一般的能力,而且只有两种形式,即:can, couldbe able to 则主要指具体做到了某件事的能力，其形式主要是靠be 发生变化，所以形式比can 多可以说：I can swim. I am able to swim. 但是不能说：All the people could escape from the big fire in time. 只能说：All the people were able to escape from the fire in time.can能表猜测，be able to不能。can的这种用法主要用于疑问句和否定句。如：Somebody is knocking at the door. Who can it be?It cant be our teacher who is knocking at the door. 其肯定形式是must be。如: It must be our teacher who is knocking at the door.could既可以用肯定形式，又可以用疑问或否定形式。如果用could表示现在“可能”，比can语气更加委婉。Could you help me with my English?3. Must 和 have to的区别 两词都是必须的意思，have to 表示客观的需要， must 表示说话人主观上的看法，既主观上的必要。My brother was very ill, so I had to call the doctor in the midnight.我弟弟病得很厉害，我只得半夜里把医生请来。(客观上需要做这件事) He said that they must work hard. 他说他们必须努力工作。（主观上要做这件事）have to有人称、数、时态的变化，而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。 He had to look after his sister yesterday.在否定结构中： dont have to 表示“不必” mustnt表示“禁止”， You dont have to tell him about it. 你不一定要把此事告诉他。 You mustnt tell him about it.你一定不要把这件事告诉他。4. Should 和 ought to 的区别 should和ought to表示责任、建议或劝告，翻译为“应该” ，ought to语气强一些 You should listen to the doctors advice if you want to recover soon. 你必须听从医生的建议如果你想赶紧康复。 Such things ought not to be allowed. 这样的事情是不背允许的。 should接动词的完成式，是一种谴责，表示过去应该做而没有做或过去做了而不应该做。 You should have finished your homework.你应该已经完成作业了。（事实上你没有完成。）ought to的否定就表示做某事一定是错误的，而should的否定就表示某动作不一定要做。ought to的否定形式是ought后直接加not构成，其否定形式可缩写为oughtnt。 One ought not (oughtnt) to cross the street against the red light. should可以用于虚拟语态,而ought to 不能，ought to 是唯一一个可加to的情态动词【基础练习】1. Wheres Mr Li?I have something unusual to tell him. You _ find him.He_Japan.A.may not,has gone to B.may not, has been to C.cant，has gone to D.cant, has been to 2. Could I look at your pictures? Yes,of course you _.A.could B.can C.will D.might3. Where is Jack，please? He_be in the classroom.A.can B.need C.would D.must4.The boy said he had to speak English in class，but he speak it after class.A.could B. didnt have to C.might D. shouldnt 5.These books_out of the reading room.You have to read,them here.cant take B. must be taken C.can take D. mustnt be taken6. _I open the window?Its hot here.A.Must B.Shall C.Will D.Would7.Go and ask Mr Liu.He _tell you.A.may B.can C.would D.could8._you please tell me the time please?A.Shall B.Will C.May D.Might9._I try out all the ideas? No,you _.A. Must, mustnt B.Need,need C.Must,dont have to D.Must,dont10._I speak to Mr Green，please?A.Will B.Could C.Must D.Would情态动词拓展练习1. It is usually cold in my hometown in March, but it _ be rather hot sometimes. A. must B. can C. should D. would2. You _ be hungry already - you had lunch only two hours ago! A. wouldnt B. cant C. mustnt D. neednt- What do you think we can do for our aged parents?- You _ do anything except to be with them and be yourself. A. dont have to B. oughtnt to C. mustnt D. cant4. John promised his doctor he _ not smoke. And he has never smoked ever since. A. might B. should C. could D. would5. What a pity! Considering his ability and experience, he _ better. A. need have done B. must have done C. can have done D. might have done6. Liza _ well not want to go on the trip, because she hates traveling. A. will B. can C. must D. may7. She _ have left school, for her bike is still here. A. cant B. wouldnt C. shouldnt D. neednt 8. According to the air traffic rules, you _ switch off your mobile phone before boarding. A. may B. can C. would D. should9. - I cant find my purse anywhere. - You _ have lost it while shopping. A. may B. can C. should D. would10. -. The light is on. We _ have forgotten to turn it off before we went out. A. should B. must C. could D. might11.- What sort of house do you want to have? Something big? - Well, it _ be big. A. mustnt B. neednt C. cant D. wont12.- What does the sign over there read. - “No person _ smoke or carry a lighted cigarette, cigar or pipe in this area.” A. will B. may C. shall D. must13. Youd better _ your hair _ once a month.A. had; cut B. had; cutted C. have; cut D. have; cutted14.You_ ask that man over there. Maybe he knows the way. A. had better not to B. had not better C. had better D. had better not15. -Can you speak Japanese? -No, I_.A. mustnt B. cant C. neednt D. may not16. Would you open the window please ? Yes, I_.A. will B. Would C. do D. can17. A lion only attacks a human being when it is hungry.A. should B. can C. will D. shall18. -Must I finish this novel this morning ? -No, you_.A. mustnt B. might no