问句 肯定回答 否定回答
Need you??Yes, I must. No,I needn‘t Must you??Yes, I must. No, I needn’t. /don’t have to.
May I ?? Yes, of course. No, you mustn’t.
Could you?? Yes, you can. No, you can’t.回答时千万不能用
Yes,you could. No,you couldn’t.
七.情态动词表猜测
must 用于肯定句
can 用于否定句或疑问句
May 用于肯定句或否定句
should 用于肯定句 八.表示推测的用法
can, could, may, might, must 皆可表示推测，其用法如下： 1）情态动词+动词原形。
表示对现在或将来的情况的推测，此时动词通常为系动词。I don't know where
she is, she may be in Wuhan.
2）情态动词+动词现在进行时。
表示对现在或将来正在进行的情况进行推测。
At this moment, our teacher must be correcting our exam papers.
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这时，我们老师想必在批改试卷
3）情态动词+动词完成时。
表示对过去情况的推测。
We would have finished this work by the end of next December.明年十二月底前我们很可能已完成这项工作了。The road is wet. It must have rained last night.地是湿的，昨天晚上一定下雨了。
4）情态动词+动词的现在完成进行时。
表示对过去正在发生事情的推测。
Your mother must have been looking for you.你妈妈一定一直在找你。
5）推测的否定形式，疑问形式用can't, couldn't表示。 Mike can't have found his car, for he came to work by bus this morning. 迈克一定还没有找回他的车，因为早上他是坐公共汽车来上班的。
注意：could, might表示推测时不表示时态，其推测的程度不如can, may。
九.情态动词+ have +过去分词
1) may(might) have + done sth, can (could) have + done sth表示过去，推测过去时间里可能发生的事情。
Philip may (might) have been hurt seriously in the car accident.Philip can (could) have been hurt seriously in the car accident.
2) must have +done sth，对过去时间里可能发生的事情的推测，语气较强，具有\肯定\，\谅必\的意思。-
--Linda has gone to work, but her bicycle is still here.
---She must have gone by bus.
3) ought to have done sth, should have done sth.本应该做某事，而事实上
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并没有做。否定句表示\不该做某事而做了\。You ought to (should) have been more careful in this experiment. He ought not to have thrown the old clothes away.（事实上已扔了。）
ought to 在语气上比should 要强。
4) needn't have done sth 本没必要做某事
I dressed very warmly for the trip, but I needn't have done so. The weather was hot.
5) 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.
十.带to 的情态动词
带to 的情态动词有四个：ought to, have to, used to, be to, 如加上have got to ,(=must), be able to为六个,它们的疑问，否定形式应予以注意：
Do they have to pay their bill before the end of the month? She didn‘t use to play tennis before she was fourteen. You ought not to have told her all about it. Ought he to see a heart specialist at once.?
例：Tom ought not to ___ me your secret, but he meant no harm.
A.have told B.tell
C.be telling D. having told
一．【语法过关】基础巩固(附答案)
1．— ______ I fill in the check-in form right now, sir? — No, you needn’t. You can complete it this afternoon.
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A. May B. Can C. Would D. Must 2． —Could I go to the movie this weekend，Dad? 一Yes，you____．But you have to come back before nine． A．shall B．must C．need D．can D. wouldn't 3．You play with fire, Tom. It's dangerous. A. needn't B. may not C. mustn't 4．As we know, fish ___die out of water. A. may B. is going to C. can D. will 5．— Shall I book some seats for the concert? —_____________. I’ve already done that. A. Yes, you may B. No, you mustn’t C. No, you needn’t D. I’d rather not 6．—I think Miss Gao must be in the library. She said she would go there. — No, she ________ be there. I've just seen her there. A. can't B. mustn't C. needn't 7．You ______ worry about him. He will get well soon. A. needn't B. can't C. mustn't D. may not D. wouldn't 8．Schools _____allow students at least one hour a day for sports． A．would B．might C．should D．could 9．You ___ open the door before the train gets into the station. A. don't have to B. mustn't C. needn't D. may not 10．—I was told to be here before eight. —Oh ,you . I’m sorry for not telling you that we have changed the plan. A．must B．can’t C．may D．needn’t 11．—May I take this book out of the reading room? — .Please read it here. A．Certainly B．No, you needn’t C．No, you mustn’t 12．—Who’s that woman with Ann? —I’m not sure. It be her mother A, may B, can C , will D, must 12
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