情态动词讲义I.情态动词的语法特征 情态动词本身虽有词义，但只表示说话人的看法，命令，准许等；不能单独作谓语，须与实义动词构成谓语1）情态动词 除ought to，have to， used to外，其它情态动词后面只能接不带to 的不定式。2）情态动词没有人称，数的变化，即情态动词第三人称单数不加-s。3）情态动词没有非谓语形式，即没有不定式to，分词-ing,-ed等形式。4）情态动词类别：can/cannot/can not/can’t, may/may not, must/ mustn’t, shall/shall not/ shan’t, should/ shouldn’t, ought to/ oughtn’t to, will/ won’t , would/ wouldn’t. need/ needn’t, dare/daren’t, used to/ usedn’t to/ didn’t use to, have to/ don’t have to, had better/ had better not, would rather/ would rather notII. 一些容易混淆的用法1.比较can 和be able to1）can/could 表示能力(born ability, learned ability), 只用于现在式和过去式(could)。 be able to可以用于多种时态。People can speak.He can speak English fluently.A computer can’t think for itself. It must be told what to do.He said he could do the work by himself.　 cf: They will be able to tell you the news soon. 他很快就能告诉你消息了。He said he would be able to get a passport soon.He had been able to speak a little Chinese before he came to China.2）只用be able to 　表示经过努力或在一定条件下设法成功地做了某事时，而非能力，只能用was/were able to， 不能用could。-----managed to do sth./ succeeded in doing sth.　　　He was able to flee Europe before the war broke out.　　= He managed to flee Europe before the war broke out.After two years of hard work, he was able to speak English.Although the driver was badly hurt, he was able to explain what had happened.With the help of the firemen, they were able to leave the burning house.3) could不表示时态(1) 提出委婉的请求，（注意在回答中不可用could）。　　 --- Could I have the television on?　　 --- Yes, you can. / No, you can't.II. 比较have to和must1)　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 middle of the night.　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)　　 I want to take more exercise, so I must walk to school every day.2） must 表示必须，必要，一种义务，责任，职责,命令等语气 e.g. We must obey the school regulations. You must respect the old. You must come here early tomorrow. I am afraid I must be leaving. We must stay home, mustn’t we?3）表示必然，必定,不可避免的结果 Man must die.表示固执，一定要，坚持要 e.g. Our three-year-old boy must do the opposite to what we ordered. Why must you interrupt me now and then while I am speaking. Must you shout so loudly?表示过去的不巧，偏偏 e.g. Just when I was busy, the neighbor must come and chat.As I was sitting down to dinner, the telephone must ring. 4）have to有人称、数、时态的变化，而must只有一种形式。e.g. He had to look after his sister yesterday.You will have to go there alone.5）must 问句的回答e.g. Must I wait until they come?---Yes, you must.

　 I would rather stay here than go home. = I would stay here rather than go home.典型例题----Shall we go skating or stay at home?----Which ___ do?　　　　　 A. do you rather　　B. would you rather　 C. will you rather　 D. should you rather答案B。本题考查情态动词rather的用法，would rather +do sth 意为"宁愿"，本题为疑问句，would 提前，所以选B。XII. 一些特殊含义和用法1．may1) may 放在句首，表示祝愿。 May the world be full of love. May God bless you!2) may 可用于让步状语从句中. Whatever faults he may have, selfishness is not one of them. However much he may admire her, he will never ask her to be his wife.3) may/might as well，后面接不带to 的不定式，意为"不妨"。If that is the case, we may as well try. (cf: might do well to do sth. , had better do)2. can 的惯用语1）can but do …只好 We can but do our best. 我们只好尽全力了2）cannot( choose / help) but do 不得不 ( can’t help doing) I can’t help but admire your courage. I can’t choose but realize that I am wrong.3）can’t help doing不禁 I can’t help liking her though she can be annoying sometimes.4）can’t …too 无论…也不过分,越…越好 We can’t be too careful while driving.5)as …as can be 。。。 得不能再，极为She is as happy as can be. 她再快乐不过了 6) as…as one can ----as…as possible3.would 的一些习惯用语。 Would you do….? Would you do me a favor? If you would…? = please If you would wait for a moment? Would you mind…?Would you mind closing the door?c.f. Would you mind my closing the door?Would you mind if I close the door? Would you please (not) do….?Would you please have the table cleared up? Would you like sth/ to do…?Would you like to go to the cinema with me?Would you like a cigarette?would like to have done sth　 本打算做某事　　I would like to have read the article, but I was very busy then.能推测背后所含的条件时，有时省略条件从句She would be shocked to hear the truth.A man of good sense would not laugh in such a case.典型例题1）---Could I borrow your dictionary?　　---Yes, of course, you____.　 　 A. might　B. will　 C. can　 D. should　 答案C.could表示委婉的语气，并不为时态。答语中of course，表示肯定的语气，允许某人做某事时，用can和 may来表达，不能用could或might。2）---Shall I tell John about it?　　---No, you ___. I've told him already.　　　 A. needn't　　B. wouldn't　　C. mustn't　　D. shouldn't　 答案A。needn't 不必，不用。 wouldn't 将不, 不会的。 mustn't 禁止、不能。 shouldn't　不应该。本题为不需要，不必的意思，应用needn't。3）---Don't forget to come to my birthday party tomorrow.　　---______.　　A. I don't　 B.　I won't　 C. I can't　D. I haven't 　　答案B.　will既可当作情态动词，表请求、建议、也可作为实义动词表"意愿、意志、决心"，本题表示决心，选B。　Tom ought not to ___ me your secret, but he meant no harm.　 　A. have told　B. tell　C. be telling　D. having told　答案A。由于后句为过去时，告诉秘密的动作又发生在其前因，此地应用过去完成时，但它在情态动词 ought to 后，所以用have。4)Be quick! They ______ for us at the school gate now.a. must have waited b. must wait c. must be waiting d. ought to have wait5)It’s getting dark, so we _____.a. should stay outside b. had better not to leavec. might as well leave d. ought to be left6)He _____ the championship, but he got injured five minutes after the game started.a. might win b. might have won c. can win d. can have won7)We _____ last night, but we went to the concert instead.a. must have studied b. might study c. should have studied d. would study8)The fire spread quickly but everybody ____ escape in time.a. was able to b. would c. could d. might9)Did you criticize him for his mistakes?Yes, but _____ it.a. I’d not rather do b. I’d rather not have done c. I ought not to do d. I’d rather not do10)I’ve tried many times, but the car just _____.a. won’t start b. wouldn’t start c. doesn’t start d. didn’t start

讲义很全面，很实用，我用了，谢了