情态动词和虚拟语气全攻略

 

 1.考查情态动词的基本用法                                                                  

①shall用于一、三人称疑问句表示征求对方意见；用于二、三人称陈述句表示说话人给对方的命令、警告、允诺或威胁等；may表示“允许、可以”，语气比较委婉。

②must用于疑问句，表示责备、抱怨的感情色彩，意思为“偏偏，偏要”，mustn’t表示禁止，是说话人强有力的劝告。cannot 表示“不可能”；need not 表示“不必要”；may not 表示“可能不，可以不”。

③needn’t表示“没有必要”

④would表示过去反复发生的动作或某种倾向

⑤表示经过努力而成功的某一次动作，只能用was/were able to,而不能用could；could还可以表示过去的某种能力

⑥考查情态动词用作答语的情况

2.考查情态动词+动词不定式一般式表推测的用法

①肯定的推测一般用must,should,may(might)或could(不用can)，其中，must的语气最强，译为“肯定”、should的语气次之，译为“很可能”、“应该”；按常理推测的may(might),could语气最弱，译为“也许”。

②否定的推测：语气不很肯定时，常用may not,might not或could not，译为“可能不”“也许不”；否定语气较强时，则用can’t，译为“根本不可能”、“想必不会”，表示惊异、怀疑的感情色彩

③疑问句中推测往往用can或could

3.考查情态动词+动词不定式的完成式表推测的用法

4.考查情态动词+动词不定式完成式的其他用法

①should(ought to)+不定式的完成式：本来应该做而实际上又没有做。其否定形式表示某中行为不该发生却发生了。

②needn’t+不定式的完成式：本来不必要做的而实际上又做了

③could+不定式的完成式：本可以做而实际上未能做,含有遗憾的意味

虚拟语气

1.虚拟条件句的基本结构及其用法

     ①与现在事实相反的虚拟条件句

     ②与过去事实相反的虚拟条件句

③与将来事实相反的虚拟条件句

2.虚拟语气的活用

   ①时间错综虚拟结构

②省略if的虚拟结构

③并列连词或副词暗示的虚拟结构

④介词或介词短语暗示的虚拟结构

⑤as if / as though方式状语从句中的虚拟语气

⑥名词性从句中的虚拟语气 

⑦分词短语暗示的虚拟结构

⑧上下文语境中的虚拟结构

【知识点归纳】

I.情态动词

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.

    A.can’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     D.can’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。

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           C.can         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     B.can’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?

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？

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？

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。

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！

7.shall/should

	用于人称	意义
shall	第一、三人称	征求对方的意见
	第二、三人称	说话人给对方的警告、命令、允诺、威胁
	用于法律、法规等条文中	应……，须……，得……

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。

should	意义
	①（表义务、责任的）应该
	②（表预期的）应该会，想必会，一定……会把
	③（表惊讶、遗憾的）竟然、居然
	④（与疑问词连用，表意外、惊讶、纳闷等的）究竟是，到底
	⑤（用于表示命令、建议、请求等词后面的that从句中，且should可以省略）应该，必须

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.

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?

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?

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。

11.其它情态动词

    ①have to

have to表示 “必须, 不得不”, 在这个意义上与must很接近, 但must表示的是说话人的主观看法, 而

have to表示的却是客观需要. have to比must有更多的形式。

The TV set is broken. I have to buy a new one.

The students will have to know how to use the computers.

注意：在回答must的问句时, 否定式常用need not(needn’t)或don’t have to表示 “不必”。而不用

must not, 因为must not表示 “不可以”。

   ②used to

表示过去的习惯动作或状态(现在已不复如此)

—Did you use to go there to see your brother? /Used you to go there to see your brother?

—Yes, I did(used to). /No , I didn’t (usedn’t).

注意：would也可表示过去反复发生的动作或某种倾向，但是不涉及到现在。

③had better

表示 “最好(做……)”

We had better go now. 

     其否定式为had better not

II.虚拟语气

（一）一般虚拟结构   

类别	用法		例句
If引导的条件从句	与现在事实相反	从句动词：过去式（be用were） 主句动词：should/would/could/might+动词原形	If he were here, he would help us.
	与过去事实相反	从句动词：had+过去分词 主句动词：should/would/could/might+have+过去分词	If I had been free, I would have visited you.
	与将来事实相反	从句动词：过去式 / should+动词原形 / were+不定式 主句动词：should/would/could/might+动词原形	If it should rain tomorrow, we would not go camping.

注意:主句中的should只用于I、we，但在美国英语中，should常被would代替；从句中的should可用于各种人称，且不可以被would所代替。

（二）混合虚拟结构

1.不同时间的虚拟

If he had listened to me, he would not be in trouble now.（从句与过去事实相反，主句与现在事实相反）

If he had told me yesterday, I should know what to do now. （从句与过去事实相反，主句与现在事实相反）

If I were you, I would have gone to her birthday party. （从句与现在事实相反，主句与过去事实相反）

If you hadn’t lent me some money, I couldn’t have bought the new house and most likely I would be still living in the dangerous house now. （从句与过去事实相反，and后面的主句与现在事实相反）

2.虚拟与陈述的混合

He could have passed the exam, but he wasn’t careful enough.

You should have come earlier. The bus left a moment ago.

（三）特殊句式虚拟结构

1.省略连词if。在书面语中，如果虚拟条件从句中有were，had 或 should，可以把if省略，把这几个词放到主语之前，构成主谓倒装。

 Should he come (If he should come), tell him to ring me up. 他要是来了，让他给我打个电话。

Were I you (If I were you), I would not do it. 我要是你，就不做这事。

2.suggest, order, propose, request, require, demand, advise, insist+ 宾语从句(should )do

He suggested that we (should) save money for the future.

The undergraduate insisted that he (should) go to work in the south.

注意：当suggest表示暗示，insist表示坚持观点,事实时，后接的宾语从句应当用真实语气。

His silence suggested that he agreed with my decision.

He insists that doing morning exercises does good to people’s health.

3.It is suggested/advised/ordered/requested/required…+ that从句(should) do

It is proposed that more students should go to university.

4.My advice/suggestion/request/requirement/order/proposal…+ is +表语从句(should)do

My advice is that you should practise speaking English as often as possible.

The order from the commander was that the troops should set off for the front immediately.

5.His suggestion/advice/request/requirement…+ 同位语从句(should )do+ is..

   The request that they should get more is reasonable.

6.It is natural/necessary/strange +that从句 (should) do表惊奇、怀疑、惋惜、不满、理应如此等。

    It’s strange that he should have missed the train. （表竟然）

    It is important that we should learn from others.（表理应如此）

    It is a pity that he should not go with us.(表惊讶、不满)

7.wish + that clause (did/were 与现在相反)

    wish + that clause (would/could/might + do与将来相反)

    wish + that clause ( had done 与过去相反)

    I wish I could go with them tomorrow.      

I wish I had never met him.

8.It is (high/about) time + 从句(did或should do )

It is (high/about) time we went home.

9.would rather + clause (did 与现在或将来相反)；（had done 与过去相反）

I would rather you came tomorrow.

I would rather you hadn’t told her the news.

10.省去条件从句或主句：表示虚拟语气的主句或从句有时可以省略，但其含义仍可以推知。

①省去条件从句

You could have washed your clothes yourself. 你本可以自已洗衣服的。

省去了"If you had wanted to")(事实是:你自己没洗衣服，因为你不想洗。)

②省去主句(常用以表示愿望) If only + clause ( did/were与现在相反)/ (would/could/might + do与将来相反) /( had done 与过去相反) “要是…….就好了“       

If my grandmother were with me! 如果我的祖母与我在一起多好啊!(事实是:祖母已不在世。)

If only she had not left! 如果她没走就好了!(事实是:她已经走了。)

If only he would come tomorrow!

If only I had taken her advice!

If only I were ten years younger!

注意：only if是“只要”的意思，从句中用陈述语气。

11.as if + clause (did/were 与现在相反) / (would/could/might + do与将来相反)/( had done 与过去相反)

She treats Kate as if she were her own daughter.

They talked as if they had been friends for years.

12.would like/was/were to have done something

I would like to have attended the party, but one of my friends came to see me.

13.but for+名词

But for your help we couldn’t have succeeded in the experiment. 

14.注意虚拟条件从句的特殊形式

Without electricity, human life would be quite different today.

Without the air to hold some of the sun's heat, the earth at night would be freezing cold.

15.注意转折语气连词引导的虚拟语气

He hesitated for a moment before kicking the ball, otherwise he would have scored a goal.

I told Sally how to get here, but perhaps I should have written it down for her.

The captain kept calm in the terrible storm, otherwise the accident wouldn't have been prevented.

Yesterday, Jane walked away from the discussion. Otherwise, she might have said something she would regret later.

16.注意分词和独立结构引导的虚拟语气

Given more than two hours, we could have done the work better.

Not having finished the work, he couldn't have seen this film.