Grammar and usage(1): Modal verbs: general introduction教学评价实录

情态动词与虚拟语气

情态动词的基本用法

情态动词具有一定的词义，没有人称和数的变化，必须和其他动词一起构成谓语，用来表示愿望、态度或推测等。

You may use my dictionary.你可以使用我的字典。(表示“允许”) You can’t have seen him just now. He has been abroad for nearly a month. 你刚才不可能看见他了，他已经出国近一个月了。(表示“推测”) 1．表示能力

can(1)表示现在的能力

am/is/are able to

(2)表示将来的能力：will be able to (3)表示过去的能力

could表示过去的能力，不表示是否做 was/were able to表示过去有能力做并且成功地做了，

相当于：managed to do sth./succeeded in doing sth.could have done 表示过去本来能够做但未做I can’t promise anything, but I’ll do what I can. 我不能许诺什么，但我会尽力而为。(表示现在的能力) If you have a good sleep, you will be able to work out this problem. 如果你好好睡一觉，你将能够解出这道题。(表示将来的能力) The fire spread through the hotel very quickly but everyone was able to get out. 尽管这场大火迅速蔓延到了这个宾馆，但是每个人都逃了出去。(表示过去有能力做并且成功地做了) I could have worked out the problem, but I was too nervous. 我本来可以解出这道题，但我太紧张了。(表示本来有能力做但未做) 2．表示推测(可能性) 可能性可分为客观的可能性和具体事情实际发生的可能性两种。

(1)客观的可能性并不表示具体某事是否会发生，而用来说明人或事物的特征。情态动．．．．．．．．．词can可用于肯定句中表示客观的(或理论的)可能性，而表示具体事情实际发生的可能性时， can一般不用于肯定句。

Accidents can happen on such rainy days. 在这样的多雨天气里可能会发生事故。(表示客观的可能性)

We may go to the cinema tonight, but we are not sure yet. 今晚我们可能去看电影，但还没确定。(表示实际可能性，不用can) (2)表示具体事情实际发生的可能性

表示具体事情实际发生的可能性的层次(由强及弱)比较：

词形

must should ought to can 肯定式

必定，必然

按说应该

按说应该

/ 否定式

/ 应该不会

应该不会

不可能

疑问式

/ / / 有可能吗？

语气比can弱

/ could 微弱的可能

或许，也许，

不可能

may 也说不定

比may还弱

可能不

比may not还弱

might

/ ①在肯定句中表示推测(must/have to, should/ought to, may, might, could) a．当说话者表达怀疑或犹豫之意时，需用may, might或

could, 其中might, could比may所表达的怀疑或犹豫之意更强。

That may be our taxi now!现在那辆可能就是我们的出租车了！

That could/might be our taxi (but I doubt it)．那辆有可能是我们的出租车(但我有所怀疑)。

b．当说话者表达毫无疑问的结论时，需用must和have to (较通俗)，意为“一定，肯定”；should和ought to所表达的程度不如must强，但比may, might和could强，should/ought to表示推测出合乎理想的情况或结果，意为“按说应该”。

He must/has to be the wanted man: He’s exactly like the one in this picture. 他一定是被通缉的那个男子：他和这张照片上的人一模一样。

He ought to/should be here on time — he started early enough. 他应该按时到这里——他出发得够早的。

②在否定句中表示推测(may not, might not, shouldn’t, can’t, couldn’t) 否定语气较弱时，常用should not (应该不会)，或用may not, might not (可能不，也许不)；否定语气较强时，则用can’t或couldn’t (不可能)。

Don’t worry. Your father may not have been hurt seriously. 别担心，你父亲也许伤得不厉害。

．．．

There shouldn’t be any difficulty in getting you a visa. 给你弄个签证应该不会有什么困难。

．．．．③在疑问句中表示推测(can, could) can, could在疑问句中，常表示困惑、不相信等。

There’s someone outside — who can it be? 外面有人——会是谁呢？

What can they be doing? 他们可能在干些什么呢？

Could he be serious? 他是当真的吗？

Where can she have put it? 她能把它放在哪儿呢？

3．表示必要性、义务、责任

(1)表示必要性

don't have to do sth.现在或将来不必做某事

needn't do sth.过去没必要做某事但做了：needn't have done sth.现在或将来必须做某事：must/have to＋do sth.

You needn’t have worked that late last night. It was harmful to your health. 你昨晚本来不必工作到那么晚的。那对你的健康有害。

—Must I give up smoking?—Yes, you must. /No, you needn’t. ——我必须戒烟吗？——是的，你必须。/不，你不必。

(2)表示义务、责任

should意为“(义务上)应该”，在语气上比must (必须)弱。“should＋动词原形”表示现在或将来应该……；“should＋have＋过去分词”表示过去本该……。

I should go and visit him this afternoon, but I wonder if I will be free. 今天下午我应该去看望他，但我不知道我是否有空。(表示将来应该) You should have come to the conference yesterday. What was the reason for your absence? 你昨天本应该参加那个会议。你缺席的原因是什么？(表示过去本该) 4．表示请求、建议、命令、允许、禁止

(1)表示请求、建议

①表示请求许可或提出建议时用：

Can Could/Will Would you ...？Shall he/she/they ...？—May I sit down？我可以坐下吗？

May/Can/Could/Shall I/we ... ？

—No, you mustn’t.不，你不可以。

Shall the driver wait outside?司机在外边等着可以吗？

Would you do me a favor?请帮我一下，好吗？

[名师指津]

请求对方许可时，could表示委婉的语气，回答时要用can。

—Could I use your bike tomorrow morning? —Yes, you can.(否定：No, I’m afraid not.) ——明天早晨我用一下你的自行车，行吗？

——行，你用吧。(否定：不，恐怕不行。) ②主动提出帮忙时用：Shall I/we ...? —What’s your name?—Aaron. Shall I spell it for you? ——你叫什么？——Aaron。我为你拼出来好吗？

(2)表示命令、允许、禁止

must (必须), mustn’t (禁止)可以表示说话者的命令或指令，语气比较强烈；should/ought to(应该), shouldn’t/oughtn’t to (不应该)也可表示说话者的命令、指令，但暗含对对方是否听从并无把握；may/might, can 表示允许。

The children must be back by 4 o’clock.孩子们必须在4点钟以前回来。

You mustn’t leave the gate open.你不要让大门敞开着。

You ought to/should apologize.你应该道歉(虽然我不知道你是否会这样做)。

You oughtn’t to/shouldn’t neglect the garden.你不应该疏于照管花园。

You may/can/might come if you wish.你想来就来吧。

Passengers may/can/might cross by the footbridge.乘客可通过步行桥穿过去。

5．表示意愿、意志、决心、允诺

(1)shall与第二、三人称连用，用于陈述句中，表示说话者的意志，用来表达说话者给对方以命令、指示或允诺。此外，当宣布法律、规定时，也用shall来表达。

It has been announced that candidates shall remain in their seats until all the papers have been collected. 已宣布，在所有试卷收上来之前，应试者必须留在自己的座位上。(规则或规定) (2)will, would与各种人称连用，用于陈述句，表示主语的意愿、意志或决心。

You can stay here as long as you can, if you will. 如果你愿意，你想在这里待多长时间就待多长时间。(表示主语的意愿) ．．—Mr. Gordon asked me to remind you of the meeting this afternoon. Don’t you forget it! —OK, I won’t. ——戈登先生让我提醒你今天下午有会议。你可别忘了！

——好的，我不会忘的。(表示决心) ．．(3)表示“宁愿做某事”时，可使用下面这些句式：

would rather do sth. than do sth.would do sth. rather than do sth.would rather sb. did sth.would rather do sth.

prefer to do sth.prefer to do sth. rather than do sth.

prefer doing sth. to doing sth.[名师指津]

高考中对这类用法的考查主要侧重结构，因此要熟记这些结构。

6．表示习惯和倾向

will (won’t)可用来叙述真理，还可叙述目前的习惯，would (wouldn’t)可以用来叙述过去的习惯。

Engines won’t run without lubricant. 没有润滑剂发动机就不能运转。

She will listen to records alone in her room for hours. 她独自一人在屋里听唱片，常常一听就是几个小时。

He would spend hours in the bathroom or on the telephone. 他以前一进洗澡间或是一打电话，往往就是几个小时。

[名师指津]

would和used to都可表示过去的习惯，但前者表示过去反复的动作，常与every day, often, frequently等连用；后者表示过去的状态或过去的习惯，但现在已不存在。

When he was abroad, he would read as many books as possible. 在国外时，他总是尽可能多读书。

She doesn’t get up so early as she used to. 她不像以前那样起得那么早了。

7．need和dare的用法

作实义

动词

作情态

动词

He needn’t do it.(情态动词) He doesn’t need to do it.(实义动词) I didn’t know whether he dared say that to him.(情态动词，有时态变化) 我不知道他是否敢对他说那些。

有人称和数的变化

无人称和数的变化

用于肯定后接to do 句、否定句、疑问句

后接动词原形

多用于否定句与疑问句

构成否定句、疑问句时要用助动词

构成否定句、疑问句时不用助动词

[名师指津]

(1)dare作情态动词时，还可用于条件状语从句中，过去式为dared；(2)作实义动词时，dare用于疑问句或否定句，后面的to也可省略；(3)I dare say是习惯说法，意为“我想，大概”。(4)need作实义动词时，还可表示“需要”，后接动名词的主动形式或不定式的被动形式表示被动含义。

He didn’t dare (to) do it.(实义动词) He dared not do it.(情态动词)

情态动词＋have done 1．对过去发生的事情或状态进行推测

must have done sth. may (might) have done sth. can (could) have done sth.

Looking at the large empty apartment, I began aware of how lonely my mother must have been in Brazil herself. 看着这个又大又空的公寓，我开始理解妈妈独自一人在巴西一定也很孤单。

The boy might have known the truth, but I am not quite sure. 那个男孩也许知道了真相，但我不是很确定。

I didn’t see her in the meeting room this morning. She couldn’t have spoken at the meeting. 我今天上午在会议室时没看见她，她不可能在会议上讲话。

2．表示“与过去事实相反”

could have done sth. needn’t have done sth. ought to/should have done sth. oughtn’t to/shouldn’t have done sth. might have done sth.

He could have gone on regretting it, as too many of us do. 他本可以继续为此而遗憾，正如我们中很多人一样。

I needn’t have taken the umbrella, for the weather is fine. 天气这么好，我本没必要带雨伞的。

过去本可以做某事但实际上没做

过去本不必做某事但实际上做了

过去本应该做某事但实际上没做

过去本不应该做某事但实际上做了

过去可能做某事但实际上没做

“(过去)一定做了某事”；语气比较肯定；用于肯定句

“(过去)可能/也许做了某事”；语气不确定；用于肯定句和否定句

“本能够做某事”；用于否定句和疑问句，表示对过去发生的行为的怀疑或不确定

You ought to have done this exercise more carefully. 你本应该更仔细地做这个练习。

You might have given him more help, though you were busy. 你本可以给他更多帮助，虽然你当时很忙。

二、

随堂过关

I. 用适当的情态动词填空。

1) My friend John ____________ to smoke, but now he doesn’t. 2) --- Could I borrow your dictionary? --- Oh, of course you ____________. 3) She __________ bring me little presents when she came to our house. 4) If you want help, let me know, ______________ you? 5)

You __________ go to Beijing by air or by train. 6)

A soldier __________ shave every morning in that country. 7)

--- Shall I tell John about it? --- No, you ___________. I’ve told him already. 8)

At that time they thought the story __________ be true. 9) It’s a secret. You _____________ tell other people. 10)

___________ you come a little earlier? II. 单项选择：

1.

He knew he ___________ tell her that. A. ought not B. ought to not C. didn’t ought to D. ought not to 2.

In those days, whenever I had difficulties, I ________ Mr. Shen for help. A. used to go to B. was used to go to C. would go to D. used to going to 3.

Who _________ to meet us but the manager! A. is coming B. will come C. should come D. has come 4.

If we had taken the other road, we ____________ earlier. A. might arrive B. had arrived C. might be arriving D. might have arrived 5.

The boy _________ the book so soon because it is difficult even to an adult. A. has finished reading B. will finish reading C. can’t have finished reading D. can’t have finished to read 6.

I was really anxious about you. You __________ home without a word. A. mustn’t leave B. shouldn’t have left C. can’t have left D. needn’t leave 7.

You can’t imagine that a well-behaved gentleman _________ be so rude to a lady. A. might B. need C. should D. would 8.

Mr. Zhang ________ come to the party, but perhaps he will go to see his father. A. must B. should C. may D. ought to 9.

--- Must I do it now? --- No, you __________. A. won’t B. needn’t C. can’t D. couldn’t 10.

Put on more clothes. You _____ be feeling cold with only a shirt on in such cold winter.

A. can B. may C. would D. must 11.

This pen ______ his; he was not here in the morning. A. mustn’t B. can not be C. should not be D. may not be 12.

The book is borrowed from a friend. You ______ you children put dots and lines here and there. A. shouldn’t be letting B. needn’t have let C. shouldn’t have let D. ought to not have let 13.

We came early and had to wait two hours before the ceremony began. We __________. A. should not hurry B. must not have hurried C. need not hurry D. need not have hurried 14.

He______ to speak with them but they appeared to be in a hurry. A. would stop B. will stop C. would have stopped D. would be stopping 15.

He didn’t even turn his head when I shouted at him. He _______ a deaf man. A. is B. should C. must be D. must have been 16.

The mother is telling her son, “You _______ eat with your fingers!”

A. wouldn’t B. hadn’t to C. mustn’t D. shouldn’t to 17.

He was a good runner so he _______ escape from the police. A. might be B. hadn’t C. was able to D. succeeded to 18.

You __________ take your umbrella. I’m sure it won’t rain. A. mustn’t B. don’t have to C. can’t D. shouldn’t 19.

Whenever my father had time, he _______ teach me English. A. used to B. was used to C. would D. could 20.

--- Need I start from the beginning? --- Yes, you __________. A. need B. do C. can D. must