高考英语语法精讲精练教师版情态动词和虚拟语气.doc

2012届新课标高三第二轮专题讲解

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等。

（一）can和could

1.表示体力或脑力(知识、技能)所产生的能力。
He could read books in English when he was only five.他只有五岁的时候就会读英文书籍了。
2.表示客观的可能性
Anybody can make mistakes.任何一个人都有可能犯错误。
3.表示请求建议，用could 比 can语气更委婉 (回答用原形)
Could you be here at eight o’clock tomorrow morning?你可不可以明天上午8点钟来这儿呢？
4.表示允许、许可，用could 比 can更委婉客气。
Could/Can I borrow your reference books?我可以借用一下你的参考书吗？

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? 难道这是真的？
You can't be serious! 你怕不是在开玩笑吧！
Oh, dear, what on earth can this mean? 哎呀，亲爱的，这究竟是意味着什么？
2.表示“经过努力后终于能……”用be able to
The fire spread the building quickly but everybody was able to escape.
大火迅速蔓延到整幢大楼，但大家都逃了出来。
注意：be able to比can有更多的形式变化
When he grows up, he will be able to support his family.他长大后就能养家了。
Frank is ill. He hasn't been able to go to school for one week.弗兰克病了，已经一周没去上学了。
I'm sorry for not being able to help you in time.对不起，不能及时帮你的忙。
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
You can not be too careful.你无论怎么小心都不为过（你越小心越好）。
4.can not but do sth. 不得不；只好。
I couldn’t but choose to wait.我只好选择等待。
（二）may和might

1.表示允许、请求。
“Might I…？”比“May I…？”语气更为委婉和有礼貌。对于“Might I …？”的回答用“… may”；
“May I …？”的否定回答常用“… mustn’t / can’t”
— May I watch TV after supper? 晚饭后我可以看电视吗？
— Yes, you may.可以。
或No, you may not.不，不可以。
或You mustn't.绝对不可以。
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.这些天也许他很忙。
He might come tomorrow.明天他也许要来的。

1.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.如果情况是这样的话，我们不妨试试看。
2.表示祝愿may而不用might。采用部分倒装语序：may＋主语＋动词原形＋……！
May the friendship between our two peoples last forever! 祝愿我们两个民族的友谊源远流长！
3.may或might可和as well连用，表示“建议”，译为“还是……的为好”
You may as well keep a certain distance from that mad man. 你们还是离那疯子远点为好。
You might as well go home now.你还是现在回家为好。
（三）must和have to
[来源:学_科_网]
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. 人人都得遵守规则。
You mustn't speak like that to your mother. 不准你那样对你母亲说话。
— Must I be home before eight o'clock? 八点之前我必须回家吗？
— Yes, you must.是的，必须的。
— No, you needn't./No, you don't have to.不，没必要/不必啦。
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.跑了这么远的路，你一定是饿了。
Home cooking must be more delicious.家常菜一定更可口。
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.现在的学生必须懂得如何使用电脑。
As he had his leg broken, he had to lie in bed.由于腿断了，他不得不躺在床上。

1.must 还表示主语主观的坚持，有“偏偏， 偏要，一定要”之意
If you must know how old I am, I tell you that I’m twice my son’s age.
如果你一定要知道我多大年龄的话，我告诉你我是儿子年龄的两倍。
2.must表示推测时的否定式是“can’t”翻译为“不可能”
Michael ______be a policeman, for he’s much too short.
A. needn’t B. can’t C. wouldn’t D. mustn’t
（四）will和would

1.用于各种人称，表示意愿或决心。will指现在，would则指过去
I will do my best to help you.我愿意尽力帮助你。
They said that they would help us.他们说他们愿意尽力帮助我们。
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。其 回 答 用“will”
—Would you pass me the book?请把那本书递给我，好吗？
—Yes, I will.好的。
Will you please give him a message when you see him? 你见到他时给他带个口信，好吗？
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.鱼儿离开了水会死亡的。
He would come to see me on Sunday when he was in Beijing.他在北京的时候，每逢星期日他常来看我。
The wound would not heal.伤口老是不能愈合。

would 与used to 的区别：
1.used 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，不与现在对比
We would sit in the yard every evening and listen to his story. (过去会这样，不与现在对比)
We used to sit in the yard every evening and listen to his story. (过去是这样的，但现在不这样了)
2.表示过去的状态，只能用used to，不能用would
There used to be a park here.这儿过去有个公园。（言下之意：现在没有了）
（五）shall, should和ought to

1.shall用于第一、第三人称作主语的疑问句中，表示征求对方（听话者）的意见
What shall we do this evening? 我们今天晚上做什么呢？
Shall he come in? 他可以进来吗？
2.should 表示“应该”，表义务，责任，也可表示劝告，建议
You should keep your promise.你应该信守诺言。
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.到了一点钟，他们该回来了。
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”
I should think you are mistaken.我倒是认为你弄错了。
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 obey your parents when they are right.父母亲对的时候，你就该服从他们。
You have practiced for a long time. There ought to be no difficulty for you.
你练了那么长时间了，对你来说，应该没有什么困难了。

1.shall用于第二、三人称表示“警告、命令、允诺、威胁”等
You shall fail if you don’t work harder.你不更加努力工作，你就不会成功。（警告）
You shall have the book when I finish reading.我读完了，你就可以拿走这本书。（允诺）
He shall be punished.他一定会遭到惩罚。（威胁）
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

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 come tomorrow. 你明天没必要来了。
— Need he come now? 他现在就需要来吗？
— Yes, he must. 是的，必须来。/ No, he needn't / he doesn't have to.不必啦。

1.“Must…？”一般疑问句的否定回答要用：No, …needn't.
— Must I finish my homework now? 我现在就必须把作业做完了？
— No, you needn’t.不，不必啦.
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.我们需要休息一下。
The house needs repairing.=The house needs to be repaired.这栋房子需要修理。
(七)dare

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.她不敢去那儿。
How dare he do such a thing? 他怎么敢做重要的事呢？
If he dare come, I will kick him out. 如果他胆敢来，我就把他踢出去。

1.惯用短语“I dare say”意为“我敢说、我想、或许”。
I dare say he is right.我敢说他是对的。
2.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.那个女孩不敢回家。
Do you dare to jump into the ocean? 跳进海洋里，你敢吗？
【注意】在否定句中时，dare后的“to＋动词原形”可以省略to。
I don't dare (to) ask her. 我不敢问她。
(八) can ,may ,must皆可用来表示推测
1.在肯定句中都可以用来表示可能。在含义上“must”语气最肯定，“may”表示的是事实上的可能性。
2.在否定句中只能用“can和may”。所以“can’t”（不可能）语气比“may not”（可能不、也许不）更强。
3.在疑问句中只能用“can”，不能用“may和must”。
①Peter ______come with us tonight, but he isn’t very sure yet.
A. must B. may C. can D. will
②Mary is in poor health. She can be ill at any times.
Michael ______be a policeman, for he’s much too short.
A. needn’t B. can’t C. should D. may
③He may be very busy now. → Can he be very busy now?
He must be very busy now. → Can he be very busy now?
④They can’t be cleaning the room now. 他们现在不可能在打扫房间。
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 done的用法
1.could+have done：过去本可以做而实际上未能做
You could have done better, but you didn’t try your best. 你本来能做得更好的，但你没有尽力。
2.cannot+have done：表示对过去行为的否定推测
He cannot have been to that town. 他不可能去过那个小镇。
3.can+主语+have done：（用于疑问句）表示对过去行为的怀疑或不肯定
Can he have got the book? 他可能得到那本书了吗？
4.might(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. 他可能没有完成工作。
If we had taken the other road, we might have arrived earlier.
如果我们走另一条路，我们可能更早地到达了。
5.must+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. 你肯定看过那部电影。
You cannot have seen the film. 你不可能看过那部电影。
6.needn’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.你本没必要浇花的，因为就要下雨了。
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.我没必要擦窗户。我姐姐两小时前刚擦过。
7.should(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. 你应该早点开始的，但是你没有。
She shouldn’t have taken away my measuring tape, for I wanted to use it.
他本不应该拿走我的字典的，因为我现在需要它。

（一）“if”虚拟条件句
主从句谓语动词的构成
情 况
从句谓语动词的构成
主句谓语动词的构成
与现在事实相反
过去式（be用were）
should/would/could/might+动词原形
与过去事实相反
had+过去分词
should/would/could/might +have+过去分词
与将来事实相反
过去式
should+动词原形
were+不定式
should/would/could/might+动词原形
注意：从句中的should可用于各种人称，且不可以被would所代替。
If he were here, he would help us.如果他在这里，他会帮助我们的。
If I had been free at that time, I would have visited you.如果那时我有空的话，我就拜访你了。
If it should rain tomorrow, we would not go camping.如果明天下雨的话，我们就不去野营。
（二）省略“if”的虚拟条件句
将虚拟条件从句中的“were，had，should”放到主语之前，构成部分倒装
Should he come, tell him to ring me up.如果他来，告诉他让他给我打电话。
Were I you, I would not do it.如果我是你，我就不做。
Had I been free, I would have visited you.如果我有空的话，我就拜访你了。
（三）混合虚拟条件句
1.不同时间的虚拟，遵守相应的规则
If he had listened to me, he would not be in trouble now.
要是他听了我的话，现在就不会有麻烦了。（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.
要是他昨天告诉我了，我就知道现在做什么了。（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.
如果我是你，我就去参加他的生日聚会了。（从句与现在事实相反，主句与过去事实相反）
2.虚拟与陈述的混合，遵守相应的规则
He could have passed the exam, but he wasn’t careful enough. 他本来能通过考试的，但他不够细心。
You should have come earlier. The bus left a moment ago. 你应该早一点来的，汽车刚走一会儿。
（四）含蓄虚拟条件句：即不用“if”而用其它形式给出虚拟条件
1.用“but for+名词”表示虚拟条件
—Did you make it at last? 你们最后成功了吗？
—Yes. But for your help, it would have caused a serious loss.成功了，要不是你的帮助，我们的损失就大了。
2.用“without+名词”表示虚拟条件
Without electricity, human life would be quite different today.
如果没有电的话，人类今天的生活就会大为不同。
3.用“动词不定式”表示虚拟条件
It would be only partly right to follow in this way. 如果这样做，仅仅对了一半。
4.用“现在分词”表示虚拟条件
Having known in time ,we might have prevented the accident.
要是及时得知的话，我们也许能阻止这场事故。
5.用“过去分词”表示虚拟条件
Given more attention, the tree could have grown better.如果多留心的话，这树本来可以长的更好。
6.用“副词otherwise”表示虚拟条件
I was too busy at that time. Otherwise, I would have called you.我当时太忙，否则我就给你打电话了。
7.用“连词but连接的句子”表示隐含的虚拟条件
He _________fatter but he eats too little.
A. would become B. would have become C. must become D. must have become
【解析】答案为A。从后句“但是他吃得太少”来看，隐含着虚拟即：如果他吃得多点，就会胖些了。
（五）特殊句式虚拟结构
1.suggest, order, propose, request, require, demand, advise, insist+ 宾语从句(should )do
He suggested that we (should)not change our mind.他建议我们不要改变主意。
He insisted that he (should) go to work in the south.他坚持要到南方去工作。
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.他的沉默说明了他同意我的决定。
He insists that doing morning exercises does good to people’s health.他坚持认为做早操对人的身体有益。
2.It is suggested/advised/ordered/requested/required…+ that从句(should) do
It is suggested that more students should go to university.有人建议应该有更多的学生去上大学。
3.My advice/suggestion/request/requirement/order/proposal…+ is +表语从句(should)do
My advice is that you should practice speaking English as often as possible.
我的建议是有应该尽可能多地练习说英语。
4.His suggestion/advice/request/requirement…+ 同位语从句(should )do+ is..
The request that they should get more is reasonable.他们得到更多的要求是合理的。
5.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. 真奇怪，这样的一个人竟然是我们的朋友。（表竟然）
It is important that we should learn from others.重要的是我们理应向他人学习。（表理应如此）
It is a pity that he should not go with us.真遗憾，他不肯跟我们一起走。(表惋惜)
6.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 were a doctor. 我希望我是个医生就好了。(现在)
I wish that the rain would stop. 我希望雨能停下来。(将来)
I wish that he had not made so much fuss about it. 我希望他不要把事情搞大了。(过去)
7.It is (high) time + 从句(did或should do )
It is (high) time we went/should go home. 我们真该回家了。
8.would rather + 从句 (did 与现在或将来相反)；（had done 与过去相反）
I would rather you came tomorrow. 我宁愿你现在呆在家里。
I would rather you hadn’t told her the news.我宁愿你没有把这个消息告诉她。
9.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 + 从句 ( 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:祖母已不在世了。)
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!要是他明天能来该多好啊！
注意：only if是“只要”的意思，从句中用陈述语气。
10.as if +从句 (did/were 与现在相反) / (would/could/might + do与将来相反)/( had done 与过去相反)
I’ve loved you as if you were my relative.我一直爱你仿佛你是我的亲人。
They talked as if they had been friends for years.他们交谈起来就像是处了多年的朋友。
注意：“as if/as though”引导的状语从句中也可以用陈述语气：当说话者认为所述的是真实的或极有可能发生或存在的事实时：
It sounds as if it is raining. 听起来像是在下雨。
He talks as if he is drunk. 从他谈话的样子来看他似乎是喝醉了。

（一）情态动词

▲can表示“能力；可能性；能够”
①If it were not for the fact that she _______ sing, I would invite her to the party.
A. couldn’t B. shouldn’t C. can’t D. might not
【解析】答案为C。“fact”后接“that”引导的同位语从句，用于对其作进一步的解释。她不会唱歌是一个事实，所以要用陈述语气。can’t意为“不会，不具备某种能力”。
②The World Wide Web is sometimes jokingly called the World Wide Wait because it _________be very slow.
A. should B. must C. will D. can
【解析】答案为D。“can”在肯定句中表示“可能性”时意为“有时候可能会”，这是它的一个特殊用法。
③We hope that as many people as possible join us for the picnic tomorrow.
A. need B. must C. should D. can
【解析】答案为D。can表示“能够”。句意：希望尽量多的人能够参加明天的野餐。need意为“需要”，表示需要或有必要做某事。must意为“必须”。should意为“应该”。
▲may表示“也许，可能”
Helen _______ go on the trip with us, but she isn’t quite sure yet.
A. shall B. must C. may D. can
【解析】答案为C。句意：海伦可能（也许）会和我们一起去旅游，但她还不能确定。根据句意我们可以推断“不是她有没有这个能力去的问题”，故不能选择D项。
▲should表示“应该；按理应该”
①—I think I’ll give Bob a ring.
—You _______. You haven’t been in touch with him for ages.
A. will B. may C. have to D. should
【解析】答案为D。should意为“应该”，多表示“某事宜做、应当做或必须做”，强调主观方面的原因。根据所提供的情景“You haven’t been in touch with him for ages.”可判断出由于多年没有联系，应该给鲍勃打电话了。will意为“将”。may意为“可以”。have to意为“因客观原因不得不做某事”。
②There ____ be any difficulty about passing the road test since you have practiced a lot in the driving school.
A. mustn’t B. shan’t C. shouldn’t D. needn’t
【解析】答案为C。根据经验或惯例对某一情况进行推测，用“should”或“ought to”，常译成“按理应该……”或“可能会……”。“shouldn’t”是其否定形式。句意：既然你已经在驾驶学校练习了那么多，要通过路考按理说不应该有什么困难的。
▲shall表示“征询对方意见；表示法律法规条文的规定”
①—What’s the name?
—Khulaifi.
—_______I spell that for you?
A. Shall B. Would C. Can D. Might
【解析】答案为A。“shall”用于征询对方的意见。此句意为：要不要我给你拼出来? “would”用于第二人称，表示“愿意”。“can”用于征得对方的同意意为“可以，可能”。“might”用于征得对方的同意意为“可以”，用于疑问句和建议时比“may”更委婉和礼貌。
②一What does the sign over there read?
一No person ________smoke or carry a lighted cigarette，cigar or pipe in this area.
A. will B. may C. shall D. must
【解析】答案为C。“shall”常用于第二，三人称表示命令，意为“必定，一定，应该”。
▲must表示“主观意愿”意为：“一定要”；表示“命令或要求”意为“必须、一定”。
①In crowded places like airports and railway stations, you___ take care of your luggage.
A. can B. may C. must D. will
【解析】答案为C。根据句意“在诸如飞机场和火车站那样拥挤的地方，你一定要看好你的行李。”must表示“必须，一定”；can和may表示“可能”。
②—Could I have a word with you, mum?
—Oh dear, if you _______.
A. can B. must C. may D. should
【解析】答案为B。must表示“一定要”表示主观意愿。can表示“有能力”；may表示“可能、也许”；should表示“应该”。
▲have to表示“客观”上的“不得不”
①—What do you think we can do for our aged parents?
—You _______do anything except to be with them and be yourself.
A. don’t have to B. oughtn’t to C. mustn’t D. can’t
【解析】答案为A。句意：除了和他们待在一起,其它的什么都不必做。mustn’t表示“禁止，不许可”的意思。
②Some aspects of a pilot’s job _______be boring, and pilots often ________work at convenient hours.