第6讲情态动词和虚拟语气.doc

第6讲 情态动词和虚拟语气（要点透析）
情态动词
情态动词表示说话人的语气和情绪，本身词义不全，不能单独作谓语，后面必须与动词原形一起构成谓语。情态动词没有人称和数的变化，有的情态动词有过去式。常见的情态动词有can, could, may, might, must, have to, shall, should, will, would, ought to, need, dare, used to等。
一、 情态动词的基本用法
(一) can, could的用法
1．表示体力或脑力(知识、技能)所产生的能力。
Her mother can speak French.
He could read books in English when he was only five.
2．表示客观的可能性。
Anybody can make mistakes.
Man can not live without air.
3．表示请求建议，用could 比 can语气更委婉。(回答用原形)
Could you wait a few days for the money?
Could you be here at eight o'clock tomorrow morning?
4．表示允许、许可，用could 比 can更委婉客气。
Could/Can I borrow your reference books?
You can smoke in the entrance hall.
【疑难点击】
1. 否定句、疑问句和感叹句中，表示怀疑、惊异、不相信的态度。
Can it be true?
You can't be serious!
Oh, dear, what on earth can this mean?
2. 表示“经过努力后终于能……”用be able to。
They were able to put out the fire without any help from the firefighters.
【疑难点击】
3. 惯用形式“can not (can't)…too/over/enough”。表示“无论怎么……也不(过分)”，用来加强语气。can not but do sth. 不得不；只好。
You can not be too careful.
I couldn't but choose to wait.
(二) may, might的用法
1. 表示允许、请求。
Might I…？ 比 May I…？ 语气更为委婉和有礼貌。
— May I ask you a question?
— Yes, please.
— May I watch TV after supper?
— Yes, you may.或No, you may not/ You'd better not./ You mustn't.(强烈的禁止语气)
2. 表示可能性，表示“或许”，“大概”。用于肯定句或否定句中，用might 比 may语气更加不肯定。
He may be very busy these days.
He might come tomorrow.
【疑难点击】
1. may, might用于目的状语从句中，含“为了……”或“以便……”之意。
Study hard that you may work better in the future.
They set out early so that they might arrive in time.
2. 惯用形式 may (might)as well＋动词原形：不妨做……
If that is the case, we may as well try.
Now that they were all here, she might as well speak her mind.
【疑难点击】
3. 表示祝愿(不用might)。采用部分倒装语序：may＋主语＋动词原形＋……！
May you succeed!
May the friendship between our two peoples last forever!
(三)must，have to的用法
1. must 表示“必须”。强调主观看法，只有现在时形式，否定式是must not(mustn't)，表示“禁止”，“不准”。
Everybody must obey the rules.
You mustn't speak like that to your mother.
— Must I be home before eight o'clock?
— Yes, you must. / — No, you needn't./No, you don't have to.
2. must表示有把握的推测，意为“一定，肯定”，用于肯定句中。　　
You must be hungry after the long walk.
Home cooking must be more delicious.
3. have to表示“必须，不得不”，着重强调客观需要，能用于更多时态(过去式和将来式)。
The students today will have to know how to use computers.
As he had broken his leg, he had to lie in bed.
【疑难点击】
must 有“偏要、硬要”之意。
— How old are you, madam?
— If you must know, I'm twice my son's age.
(四)will，would的用法
1. 用于各种人称，表示意志或决心。will指现在，would则指过去。
I will do my best to help you.
They said that they would help us.
2. 用于第二人称的疑问句中表示有礼貌的询问和请求，would 比 will更委婉。
Would you teach us how to drive a car?
Will you please give him a message when you see him?
3. 表示习惯性、经常性、倾向性，意为“总是”，“惯于”。 will指现在，would指过去。
Fish will die without water.
He will sit for hours reading.
He would come to see me on Sunday when he was in Beijing.
【疑难点击】
1. 表示说话人的推测，意为“大概，也许”。would 的肯定性不如will强，语气比较弱。
That will be the man you want to see.
Perhaps she would be willing to meet us.
2. 表示功能，译作“能”或“行”。
That will do.
The machine won't work.
He tried the door again, but it wouldn't open.
【疑难点击】
3. would 与used to 的区别：
①used to 表示过去的某种习惯，现在已经没那样的习惯了；would 表示过去有某种习惯，现在可能还有。
②表示过去的状态，只能用used to，不能用would。
There used to be a park here.
(五)shall，should, ought to的用法
1. shall用于第一、第三人称作主语的疑问句中，表示征求对方的意见。
Shall I turn off the light?
Shall he come in?
2. should 表示“应该”，表义务，责任，也可表示劝告，建议。
You should keep your promise.
I should help him because he is in trouble now.
Young people should be polite.
3. should表示按常规、常理推测，意为“可能”或“应该”。
They should arrive by one o'clock.
Mother should be back by now.
4. 提出意见、请求、建议时，可用should表示委婉、谦逊的语气，意为“可”，“倒是”。
Should you like some tea?
I should think you are mistaken.
5. ought to表示责任和义务，意为“应该”，语气比 should强；还可表推测。
You ought to finish your work before you go home.
You ought to obey your parents when they are right.
You have practiced for a long time. There ought to be no difficulty for you.
【疑难点击】
1. shall 用于第二、三人称作主语的陈述句中，表示说话人的决心、意志、许诺、命令、警告、威胁等。
You shall go with me.
I promise you shall see them again.
You shall not leave your post.
2. Why/How ＋should结构表示说话人对某事不能理解、感到意外、惊异等意思，意为“竟会”。
Why should you be so late?
你今天来得怎么这么晚？
How should I know?
我怎会知道！(意为：我不知道。)
(六)need的用法
1. need作情态动词表示“需要”，“必要”。通常用于否定句、疑问句、条件句中，且只有现在时，其他时态用“have to”的相应形式代替。
You needn't water the tomato plants now.
— Need he come now?
— Yes, he must. / No, he needn't / he doesn't have to.
2. need还可以用作行为动词，其变化和一般的动词相同。若主语为动作承受者时用动词主动形式表示被动意义或用不定式的被动形式。　　
We need to have a rest.
The house needs repairing.
＝The house needs to be repaired.
【疑难点击】
“Must…？”一般疑问句的否定回答要用：No，sb. needn't.
— Must I finish my homework now?
— No，you needn't.
(七)dare的用法
1. dare作情态动词表示“敢于”，用于否定句、疑问句和条件句中。
She dare not go there.
How dare he do such a thing?
2. 惯用短语“I dare say”意为“我想，大概”。
I dare say he is right.
3. dare还可以用作行为动词，其变化与一般动词相同。
The girl didn't dare to go home.
Do you dare to jump into the ocean?
I don't dare (to) ask her.
【注意】在否定句中时，dare后的“to＋动词原形”可以省略to。
二、情态动词的其他用法
情态动词除各自有自己的词义外，还可以表示猜测和责备(虚拟)等意义。
(一)情态动词表推测的用法
can /must/may/should这四个情态动词可以用于推测，可以对现在状态、现在正在进行的动作、过去已经发生的动作或对将来发生的动作进行推测。
1．对现在状态、现在正在进行的动作的推测，用“情态动词＋动词原形”结构，不同用法如下：
(1) can
can用于否定句：意为“不可能”。
The door is locked. He can not have got home.
(2) may
(1)用于肯定句，意为“也许，可能”(might 的可能性更小)。用于否定句，意为“也许不/没有，可能不/没有”(注意与can't 否定猜测时意思的对比)。
He has a car. He may come by car, but I am not sure.
No one comes to answer the phone. He may not be at home.
(3) must
只能用于“肯定句”表示猜测，意为：“肯定，必定”(＝I am sure that…)。
(4) should/ought to
用于肯定句，意为 “理应，应当”(按常规、常理、风俗习惯等进行推测)。
It's spring now. It should be warm.
The new coat ought to be ready on Thursday.
2．对过去所发生的事情的推测，用“情态动词＋完成式”结构，不同用法如下：
(1) must have done 一定做过某事。
There's no light in the room. They must have gone to bed.
(2) cannot have done 表示对过去所发生的行为的怀疑和不肯定。
(3) could have done 本来可以做而实际上未做。
You could have done the work better.
你本来可以把工作做得更好一些的。
(4) may/might have done 也许/或许已经…… ；本来可能……(但实际上没有发生)；本来应该或可以做某事(含有轻微的责备语气)。
He may not have finished the work.
他或许没有完成这项工作。
He might have given you more help, even though he was very busy.
他也许可以给你更多的帮助，尽管他很忙。
(5) should / ought to have done 本来应该做而实际上未做。
You ought to have done the exercise more carefully.
你本应该更加仔细地做这个练习。
You should have been here five minutes ago.
你本来应该5分钟以前到这儿。
(6) ought not to have done/shouldn't have done/needn't have done 本来不应该做而实际上做了
We shouldn't have waited for her because she never came.
我们本来就不必等她，因为她从未来过。
You needn't have come over yourself. You could have given me a ring instead.
你本来不必亲自来，只要给我通个电话就行了。
【疑难点击】
1. 当must作“必须”意义时，其反意部分用needn‘t; 当含有mustn’t时，其反意部分用must/may；　　
You must go now, needn't you?
You mustn't smoke here, must/may you?
2. 当情态动词表推测时，反意部分的动词形式根据情态动词后面所隐含的时间来确定。
You must be hungry now, aren't you?
You must have heard about it, haven't you?
You must have watched that football match last night, didn't you?
虚拟语气
一、状语从句中的虚拟语气
(一) if 引导的条件状语从句 (非真实条件)
条件
从句谓语
主句谓语
与现在事实相反
过去时(be多用were)
would/should/could/might＋动词原形
与过去事实相反
had done
would/should/could/might＋have done
与将来事实可能相反
一般过去时(be多用were)或should＋动词原形或were to do
would/should/could/might＋动词原形

If I were you, I should accept the invitation.
如果我是你，我会接受邀请的。
If I had time, I would go there.
如果我有空，我就去那儿。
If you had come earlier, you couldn't/wouldn't have missed the bus.
如果你早点来，你就不会错过那辆公共汽车了。
If he had seen you yesterday, he would have returned your book.
如果他昨天见到了你，他就会还你的书的。
If it should rain/were to rain/rained tomorrow, the sports meet would be put off.
万一明天下雨，运动会就推迟。(事实上明天下雨的可能性不大。)
If you dropped/should drop/were to drop the glass, it would break.
万一杯子掉下来会打碎的。
(二)目的状语从句
1．so that/ in order that ＋从句(从句用can/could/ may/ might ＋ 动词原形)
We got up early in order that we could catch the first bus.
2．for fear that/in case that＋ 从句(从句用should＋动词原形)以防万一发生……
We got up early for fear that we should miss the first bus.
3．lest ＋从句(从句用should＋ 动词原形)以防万一发生……
We got up early lest that we should miss the first bus.
(三)方式状语从句
as if/though ＋ 从句(从句的虚拟语气与wish 后的宾语从句虚拟语气类似)
She speaks English as though she were a native of New York.
【注意】　
as if/though引导的从句也可用陈述语气。
It looks as if it is going to rain.
二、名词性从句中的虚拟语气
1. 名词性从句中，表示“建议，命令，要求”等意义时，名词性从句用(should)＋ 动词原形。
①建议— advise, suggest, propose, recommend (advice, suggestion, proposal, recommendation为名词)
②命令— order，command
③要求— request, require, demand, ask, insist (坚持要求) (request, requirement, demand为名词)
The doctor suggests I (should) exercise every day. (宾语从句)
It is suggested that I (should) exercise every day. (主语从句)
The doctor's suggestion is that I (should) exercise every day. (表语从句)
The doctor's suggestion that I (should) exercise every day sounds reasonable. (同位语从句)
【疑难点击】
1. suggest 意为“表明，暗示”时，不用虚拟语气。
insist 意为“坚持认为，坚持说”时，不用虚拟语气。
His face suggested that he was very sad.
The man insisted my little brother was a thief.
【疑难点击】
2. I wish (that )＋宾语从句 (从句必须使用虚拟语气)。
①表示愿望与“现在事实相反”，从句用一般过去时。
I wish I were you.
How he wishes that he were a bird.
②表示愿望与“过去事实相反”，从句用过去完成时。
I wish I had seen the film last night.
We wish that we had visited the Great Wall last year.
③表示愿望实现的可能性很小，从句常用could/might/would ＋动词原形。
We wish we would live on the moon one day.
【疑难点击】
3. would rather/prefer ＋ that－从句(从句用虚拟语气)。
①表示愿望与“现在事实相反”，从句用一般过去时。
I would rather you were not here with me now.
②表示愿望与“过去事实相反”，从句用过去完成时。
I would rather you hadn't done that.
【疑难点击】
4. 名词性从句表示说话人“强烈”的感情色彩，此时，从句用should ＋动词原形/should ＋ have done (表示动作在过去已经发生)，should 可译为“应该；居然，竟然”。should 可以省略。
常见的句型如下：
①It is important/necessary/ strange/ surprising/ funny/ natural ＋ that－从句
It is important that we (should) have a good knowledge of computer science.
我们应该掌握电脑知识，这是很重要的。
【疑难点击】
②It is a pity / a shame/ an honour/ no wonder that－从句
It is a pity that you (should) be absent from the meeting.
③主语 ＋ be ＋ sorry/ disappointed/ surprised ＋ that－从句
We are surprised that he (should) be a doctor.
三、定语从句中的虚拟语气
It's (about/high)time that－从句 (从句用虚拟语气，谓语用did/ should do, should 不能省略)某人该做某事了。
It's time that we should go home.
It's time that we went home.
＝It's time for us to go home.
注意对比：It/This is the first/second/…time that＋主语＋has/have done…(这是某人第几次做了某事)
It is the second time that I have visited Beijing.
这是我第二次来北京游玩。
四、含蓄虚拟语气
1. if only 要是……就好了＝ I wish…(与wish后面的虚拟语气类似)
If only you hadn't told him the news.
2. without/ but for 如果没有……
Human beings would die without water.
I couldn't have succeeded but for your help.
3. otherwise/or 否则，不然的话
I had no money then. Otherwise I would have bought that book.
4．含虚拟语气的句子，but＋真实情况
Mary would tell us something about London, but she isn't from London.
【疑难点击】
1. 含有虚拟语气的条件状语从句中，如有had，should，were这三个词的话，在正式或书面语言中可将if省略，把had，should，were 提前放到句首，变为半倒装。如：
Had they had time(＝If they had had time), they would have certainly come to help us.
Should it be fine(＝If it should be fine), we would go for an outing.
Were I you(＝If I were you), I would go.
【疑难点击】
2. 几种特殊用法
was/were supposed to have done 理应做……
was/were to have done 本计划做……
had thought/believed…， but…本以为……
had planned/intended…， but…本计划……，本打算……
had wished/hoped…， but…本希望……

第6讲 情态动词和虚拟语气（考点突破）
(　　) 1. Many women ______ a good salary, but they chose to stay at home for the family.(2011·浙江衢州市杜泽中学高三第一次模拟)
A. must make B. must have made
C. should make D. could have made
(　　) 2. You have a big mouth, Tom. You ______ have told everybody the secret.(2011·北京市日坛中学高三摸底)
A. can't B. mustn't
C. shouldn't D. mightn't
【解析】
1. D　could have done 表示本来可以做某事，而实际没做。
2. C　shouldn't have done 表示本不该做某事，而实际做了。
(　　) 3. He ______ have come here yesterday, ______ he？(2011·福建福州三中高三第一次月考)
A. mustn't; did B. couldn't; has
C. must; haven't D. must; didn't
(　　) 4. — What it ______ be?
— It ______ be a man, for it is not moving. It ______ be a dustbin, I think.
A. can; may; must B. can; can't; must
C. can; must; can D. may; may not; could
【解析】
3. D　含有must表示推测的句子改为反意疑问句时，先将此句时态根据时间进行还原，然后进行反问。由yesterday可知，用一般过去时。
4. B　根据语境，第二和三空只有can't和must可以搭配。
(　　) 5. It is high time that the child ______ to the hospital.
A. is sent B. would be sent
C. be sent D. were sent
(　　) 6. There ______ be any difficulty in passing the road test since you have practiced a lot in driving school. (2011·安徽亳州一中高三第一次月考)
A. mustn't B. shouldn't
C. shan't D. needn't
【解析】
5. D　It is high time 定语从句中的谓语多用过去虚拟语气。
6. B　shouldn't 不应该。
(　　) 7. —I wonder why Sara looks worried today.
— I'm not sure，but she ______ a small accident driving here. (2011·四川绵阳中学高三第一次月考)
A. could have B. might have
C. might have had D. must have had
(　　) 8. — I haven't got the reference book yet, but I'll have a test on the subject next month.
— Don't worry.You ______ have it by Friday. (2011·云南昆明一中高三月考)
A. shall B. could
C. must D. may
【解析】
7. C　表示对过去动作的推测，D项与I'm not sure不符。
8. A　shall 与第二人称连用，表示给对方的允诺。
(　　) 9. They ______ be at home. You see, the door is locked from the outside. (2010·河南郑州智林学校高三模拟)
A. can't B. may
C. must D. mustn't
(　　)10. She insisted that she ______ not guilty, but we insisted that she ______ into prison.(2011·江西南昌一中高三月考)
A. was; be put B. be; was put
C. should be; was put D. was; should put
【解析】
9. A　can't 不可能。
10. A　第一个意为“坚持认为”，后不与虚拟语气连用；第二个意为“坚决要求”，后要用虚拟语气，即(should)＋动词原形，根据句意，此处需用被动语态，故选A。
(　　)11. It was strange that he ______ have uttered such rude remarks on that occasion. (2011·浙江嘉兴一中高三月考)
A. must B. could
C. should D. would
(　　)12. — Can I pay the bill by check?
— Sorry, sir. But it is the management rule of our hotel that payment ______ be made in cash. (2011·甘肃天水市三中高三第一次月考)
A. shall B. need
C. will D. can
【解析】
11. C　在句型It is/was ＋strange/important/necessary/natural/essential ＋that…中，从句要用(should)＋动词原形，表示虚拟。
12. A　shall 用于第三人称，指法规中的义务和规定。
(　　)13. — What are you doing, John? Why stop?
— To be on the safe side, we'd fill up the car now for we ______ run out of gas on the way.(2010·重庆高三模拟)
A. must B. will
C. might D. should
(　　)14. ______ we would not have achieved so much. (2010·江苏盐城市八中高三模拟)
A. If they didn't help us
B. If it hadn't been their help
C. Weren't it for their help
D. Had it not been for their help
【解析】
13. C　might 可能。
14. D　在if 引导的虚拟条件句中，可以把were/should/had 提到if 的位置，构成倒装。
(　　)15. Without the air to hold some of the sun's heat, the earth at night ______ very cold, too cold for us to live. (2010·江苏南京十三中高三考前模拟)
A. will be B. would have been
C. Is D. would be
(　　)16. ______ it rain tomorrow, we would have to ______ the picnic. (2010·江苏东台市时堰中学高三考前仿真模拟)
A. Would; put forward B. Should; call off
C. Will; give up D. Should; put up
【解析】
15. D　without 短语相当于if 虚拟条件句，主句要用虚拟语气。
16. B　第一空见14题；put forward 提出； call off 取消； give up 放弃； put up 举起，搭起。
(　　)17. “It's better to pay the grocer than the doctor” was the saying that my late grandmother ______ frequently use to remind us of healthy eating. (201