10.情态动词+have done的用法

①could+have done：本可以做而实际上未能做

　　 You could have done better, but you didn’t try your best.

②cannot+have done：表示对过去行为的否定推测

　　 He cannot have been to that town.

③can+主语+have done：表示对过去行为的怀疑或不肯定

Can he have got the book?

④might(may)+ have done：对过去发生的行为不太肯定的推测

He may not have finished the work.

If we had taken the other road, we might have arrived earlier.

(Mood:might>may,possibility:might<may)

⑤must+have done：对过去发生的行为肯定的推测。其否定式为：cannot have done

You must have seen the film.

You cannot have seen the film.

⑥needn’t+have done：本来不必要做的而实际上又做了

You needn’t have watered the flowers,for it is going to rain.

注意：didn’t need to(have to)do :没有必要做而实际上也没有做

I didn’t need to clean the windows.My sister did it 2 hours ago.

⑦should(ought to)+ have done：本来应该做而实际上又没有做。

其否定形式表示某种行为不该发生却发生了。

　　 You should have started earlier, but you didn’t.

　　 She shouldn’t have taken away my measuring tape, for I wanted to use it.

　　 注意：本结构还可以表“推测”的意思

He should have finished the work by now.

到现在他应该已经做完那项工作了。

9.dare和need

①need作为情态动词只有一种形式，只用于否定句和疑问句。

②dare作为情态动词用时有两中形式：dare和dared两个词形。

　　 除了可以用于否定句和疑问句外，还可以用于条件从句或表示怀疑的句子中。

　　 If he dare come,I will kick him out.

　　 I don’t know whether he dare say.

Note:He doesn’t dare(to)answer the question.

　　 Does she dare(to)enter the dark room?

8.will/would

①请求、建议，would比will委婉客气

　　 Would you pass me the book?

②表示意志、愿望和决心

　　 I will never do that again.

　　 They asked us if we would do that again

③可表示过去反复发生的动作或某种倾向

　　 During the vacation he would visit me every week

　　 The wound would not heal.

④表示估计或猜想

　　 It would be about ten when he left home.

　　 What would she be doing there?

7.shall/should

What shall we do this evening?

注意：may用于征求对方的许可，而shall用于征求对方的意见或指示：

May I have a look?我能看一看吗？

Shall I have a look?需要我看一看吗？

You shall fail if you don’t work harder. (警告)

He shall have the book when I finish reading. (允诺)

He shall be punished.(威胁)

The fine shall be given in cash.罚款须以现金缴纳。

①You should apologize to him.

②The photos should be ready by 12:00.

③I’m surprised that you should speak in such a way.

④Who should ccome in but my old friend Betty.我当究竟是谁进来了呢，原来是我的老朋友贝蒂呀。

⑤I suggested that he (should)change his mind.

My suggestion was that he (should)change his mind.

注意：ought to表示 “应该” (与should同义, 只是语气稍重一些), 也可表示推测。

You ought to take care of him.　　　

He ought to be home by now.

6.表示祝愿、祝福的may,此时句子用倒装语序

　 May he live to an old age!愿他长命百岁！

May God be with you!愿上帝保佑你！

5.构成下列特殊句式的can

　①can not/can never…too… cannot…enough“无论怎么……也不为过分，越……越好，非常……”

Since it is a good thing,we cannot do it too soon.

既然是好事情，我们越早开始做越好。

②can’t help doing…,cannot help but do…,cannot but do…“禁不住，不由得，不得不”

I cannot help admiring the picture whenever I look at it.每当我看到这幅画时，我都禁不住要鉴赏它。

When a close friend dies,you cannot but feel sad.

亲密的朋友去世时，你会不由得感到悲伤。

4.表示“惊讶、怀疑”(用在疑问句中)的can和could，这时could比can语气更婉转

Who can it be at this time of day?这个时候到底会是谁呢？

3.表示“请求、提议”(用在疑问句中)的can和could，这时could比can语气更婉转

Can(Could)you give me a lift to the station?

你(您)能不能让我搭你(您)的车去车站呀？

2.表示“推断、判断”的can,may,must

①在肯定句中都可以用来表示可能。在含义上must语气最为肯定,may表示的是事实上的可能性：

Peter______come with us tonight, but he isn’t very sure yet.

A.must　 　　　　B.may　 　　　　　　 　　　D.will

而can表示的是逻辑上的可能性：Mary is in poor health. She can be ill at any times.

②在否定句中只能用can和may。此时can’t用以代替mustn’t，语气比may not更强。can’t中文可以翻译为“不可能”、may not中文可以翻译为“可能不”。

Michael______be a policeman, for he’s much too short.

A.needn’t　 　’t　　 　　C.should　 　　D.may

③在疑问句只能用can，不能用may和must

He may be very busy now.

Can he be very busy now?

He must be very busy now.

Can he be very busy now?

1.表示“能力、许可”的can /may

①表示能力的情态动词用can/could

　　 A computer_____think for itself, it must be told what to do.

　　 ’t　 　　　　　　B.couldn’t　 　　　　C.may not 　　　　　D.might not

②表示许可时用may/might ,can/could 都可以，但在问句中用could…?

或might…？ 以使口气委婉客气，其回答一定要用can或may，以使回答口气明确(must表示一

定，必须，mustn’t表示禁止，不许可)

-Could I call you　 by your first name?　 -Yes, you______

A.will　　　 　　　　　B.could　 　　　　　C.may　 　　　　　　D.might

Johnny, you_____play with the knife, you_____hurt yourself.

A.　　　 won’t/can’t　　　　 B.mustn’t/may 　　　C.shouldn’t/must　　’t/shouldn’t

③在肯定句中could不可以用来表示过去某一特定场合的能力，而要用was/were able to。

　　 如不可以说：They could jump into the sea before the boat was blown up

　　 而要说：they were able to/managed to jump into…

　　 The fire spread through the hotel very quickly but everyone_____get out.

A.had to　 　　　　　　B.would 　　　　　C.could 　　　　　　D.was able to

　　 但在否定句中could/was(were)able to可以通用:

　　 I couldn’t/wasn’t able to see him yeaterday.

④表示许可时用may/can都可以。只不过用may时较侧重讲话人的许可，而can较侧重客观情况的许可，must则表示必须做某事。