1、情态动词用法,一、can/may/must/need问句的回答方式：,Yes, you may/ can.,Yes, I can.,No.I cant.,No, you mustnt/may not.,Yes, you must.,No, you neednt/dont have to.,Yes, you must.,No, you neednt/dont have to.,(二）dare与 need的用法： 1、need表示“需要”或“必须”，作情态动词时，仅用于否定句或疑问句中，(在肯定句中一般用must, have to , ought to, should )如：,1)You need
2、nt come so early. 2)-Need I finish the work today?-Yes, you must.,2、dare作情态动词时，主要用于疑问句、否定句和条件句中，如：,How dare you say Im unfair?He darent speak English before such a crowd,dare he?,3、 dare与 need作实义动词， 有人称、时态和数的变化， 用法上的区别是：在肯定句中，dare后面通常接带to的不定式 ，在否定和疑问句中，后面可接带或不带to的不定式。,如：I dare to swim across this ri
3、ver.He does not dare (to) answer.,情态动词比较： （一）can与be able to 的比较can除了表示能力外，还可以表示否定或疑问的可能性，没有 人称与数的变化；而be able to 除表示能力外，还可以表示具 备了某种能力所导致的结果，有人称与数的变化和时态的变化。,Few people could/were able to send their children to school before liberation.2) -Could Lewis be in the office now?-No, he cant be, for he is ill
4、 in hospital.3) Joe was an excellent swimmer, so he was able toswim back to the bank when the ship sank.,（二） must与 have to的区别must表示“主观”的必须，没有人称与数的变化，不能与其他情态 动词或助动词连用；have to 是半情态动词，表示“客观”的必须 或“不得不”的 意义， 能与助动词连用。如：,1）It snowed heavily last night, so I had to get up early to sweep the snow in the yard
5、.2) Every student must obey the school rules and become a good student in every way.,（三）shall 与will比较,（四）used to 与would的比较,两者都可以表示“过去惯常”，其区别在于：1.would 主要表示过去一段时间内的某种习惯，常与表示过去 的时间状语连用 ，意为“总是，总要”；used to 主要表示过去 存在但是现在已经不再存在的习惯，意为“过去经常”。如：,1）On Sundays he would go to call on the old man when he was you
6、ng. I used to get up late, but now I have got used to getting up very early.,2. used to 还可以与状态动词连用，表示过去的状态，而would 没有这 种用法。下面两句只可用used to ，而不可用would.,My little sister used to like picture books. Xiao Li used to be a model worker. He is now a university student.,mustnt禁止，不准； cant/couldnt不能，不可能；may not
7、不可以； neednt 不必；shouldnt不该； wont/wouldnt不愿意； darent不敢。,(五)、情态动词的否定形式比较：,情态动词表示推测：（一）对现在的推测：,must; may/might; can/could(用于否定句或疑问句中）,（二）对过去的推测：1）must have done表想必或肯定（已经）做了 某事,The ground is rather wet, so it must have rained lastnight, didnt it?,2)can/could have done表示可能已经了吗？用于疑问句中。,Someone must have br
8、oken into our bedroom. Who could have done it?,3) may/might have done 表示“可能/大概（已经）做了某事”,Tom may have gone to Shanghai, but Im not sure about it.,4) cant/ couldnt have done表示不可能已经做了某事,The ground is very dry, so it cant have rained lastnight.,情态动词+完成式表示“责备”、“怀疑”或“遗憾”等意义：,1）should/ought to have done 表示
9、过去该做某事而没有做的情况，表示说话人后悔、遗憾或责备的语气。如：,I really regretted wasting the hours when I shouldhave studied hard. but it is too late.,shouldnt/oughtnt to have done 表示过去不该做而做了的情况. 表示说话人后悔或责备的语气。如：,Im very sorry for the words I shouldnt have said to you at that moment.,3) Could have done 表示本来能够做却没有做某事的责备语气。,-I p
10、aid a visit to New York last month and we stayed at a nice hotel. -Oh, you could have stayed with Barbara. She isalways willing to do you a favour.,4) Would rather have done表示本来想做某事却未做成的意思.,I would rather have come to help you with your English, but I was too busy at that time.,情态动词和助动词专练 1. He ough
11、t _have done so even if possible.A. not to B. to not C. not D. never A 2. It was so dark outside that he _go out alone.A. dared not to B. dared not C. dares not D. doesnt dare to B 3.Where is my ruler?-I _it.A. might lose B. would have lost C. should have lost D. must have lost D 4. If he started at
12、 seven, he _be here now. A. can B. may C. ought to D. could C 5. A computer _think for itself. It must be told what to do.A. cant B. couldnt C. may not D. might not A 6. Since the ground is wet, it _last night. A. should have rained B. has rained C. must rain D. must have rained. D,After her sons de
13、ath, the old lady _often sit at the window, deep in thought.A. would B. should C. could D. might A Post the letter for me, _ you?A. dont B. shall C. will D. do C “Could I borrow your dictionary?” “Yes, of course you _.” A. might B. will C. can D. should C A: There were already five people in the car
14、 but they managed to take me as well. B: It_ a comfortable journey. A. cant be B. shouldnt be C. mustnt have been D. couldnt have been D I _get this done immediately or it will be too late.A. can B. shall C. may D. must D,7. Would you like to see the play tonight? I _ meet you at the gate of our school.A. will B .may C. must D. ought to A,
