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情态动词的语法特征
1） 情态动词不能表示正在发生或已经发生的事情，只表示期待或估计某事的发生。2） 情态动词 除ought 和have 外，后面只能接不带to 的'不定式。
3） 情态动词没有人称，数的变化，即情态动词第三人称单数不加-s。
4） 情态动词没有非谓语形式，即没有不定式，分词，等形式。
第一部分 快乐大篷车
基本理念：只研究考点，坚决不死缠烂打。 考察掌握内容包括两点：第一部分基本语法; 第二部分情态动词特殊用法对过去的推测。
一、情态动词的基本用法 1. 常识; <1>must 它是情态动词中,语气最强的一个词汇. 否定形式：mustn't ? Needn't?
笔记:肯定句的must变为否定句时，一定要用needn't，而不是mustn't. mustn't表示必须...如何，而needn't表示不需要...如何。
注意：笔记:must与have to区别： must表示必须;have to表示不得不. must强调主观意愿上的,而have to强调客观意愿上的.
Eg: I must work hard. 我必须努力工作。(内心深处主观想法) I have to work hard. 我不得不努力工作。(客观因素造成)
<2>can、may; 含义：can表示可以或能够;may只有可以这一个含义; 区别：can't表示不可以、不可能;may not表示可以不;
Eg: You can't do this. 你不可以这样做。 You may not do this. 你可以不这么做。
<3>情态动词由语气的强到弱排列; must>can>may>might,could
<4>can't + too +adj.表示再……也不过分
Eg: You can't be too careful when crossing the road.
译文：当你过马路的时候，再怎么小心也不过分。
第二： 情态动词的比较; <1>所有的can、could与be able to区别; 区别：can、could强调的是天生的能力;(与生俱来的) be able to表示设法做成某事;(通过后天的努力)
<2>need与dare使用; 共同点：做情态动词时,只可在条件句、否定句、疑问句; 而且必须+to do;否定式直接加not即可。
2. 表示推测;(包含对现在的推测和对过去的推测) 第一 对现在的推测; <1> can的推测表示理论上的可能; <2> could的推测表示实际操作的可能; <3> may/might+(be V-ing)或动词原型;表示对现在或者未来的推测,常用在肯定句内. <4> must表推测时用法完全与may/might相同;
判断方法：利用基本的翻译理论.
第二 对过去的推测;(形式：情态动词+have+pp) 可能或不可能出题的地方：<1> pp不可能出题; <2> have 没有出题的地方; <3> 情态动词唯一出题点(含义不同)
解题方法：对立统一原则解决一切问题!!! <1>判断前后句的关系; (1) 统一;前句和后句之间说的是一回事; (2) 对立;前句和后句之间说的不是一回事;
<2>解题步骤; (1) 如果判断出是统一关系; A. 使用must + have + P.P仅从解题角度可知,解题结束; 表达含义过去一定发生过某事,口气绝对,无否定. B. 使用may/can/might/could + have + P.P; 可用在否定形式,还可用在肯定形式.
特殊之处：must不可以应用在否定句式中.
(2) 如果判断出是对立关系; A. 使用should + have + P.P;仅从解题角度,解题结束. 表达含义：过去本应该做但是实际上没有做
补充：should=ought to 否定形式：should + not + have + PP; ought not to + have + PP; 表示含义：过去本不应该做但是实际上做了
例题一、Sorry I"m late.I ____have turned off the alarm clock and gone back to sleep again. A.might B. should C.had to D.will 例题二、I told Sally how to get here,but perhaps I____ for her. A.had to write it out B.must have written it out C.should have written it out D.will have written it out.
解析：例题二 关键词汇but，说明前后为对立关系，从而可以确定使用should或ought to. 解析：例题一 由句意可知，前后为统一的关系，可以使用must、can、may、might、could,
进行对比就可知道A正确。
知识回顾： 解题方法：第一 利用基本含义套入原题,进行翻译(翻译法); 第二 统一对立原则.(主要解题对过去推测的问题)
考研英语：语法大全(情态动词特征及变化)
情态动词概述
特征
1)情态动词(modal verb)本身有词义，表示说话人的语气或情态，但词义不完全，不能单独用作谓语动词，一般只能和动词原形一起构成谓语动词。
2)情态动词所表示的情态有：命令、允诺、请求、拒绝、愿望、愿意、义务、必要、可能、能力、敢于、需要等。
3)情态动词(ought除外)和助动词shall，will，should，would一样，后面的动词不定式一般皆不带。
形式变化
1)没有人称和数的变化，第三人称单数的现在时也无变化。如：
I can We can
You can You can
He
They can
She can
It
2)有些情态动词有过去式，有少数过去式和它的.原形相同。
a)有过去式的情态动词有：
may -- would
can DD could
mayDD night
shall -- should
have to -- had to
b)过去式不变的情态动词有：
must - must (或had to)
ought to - ought to
need---need
dare - dare(亦可用dared)
3)大多数情态动词后面可用动词的进行式、完成式和被动形式，如：can(may，must)be doing，can(may，must) have done，can(may，must)be done等。
否定式
情态动词和助动词一样，后面可直接跟否定词not。现将情态动词的否定式及其否定式的简略式(简略式用于口语中)列举如下：
shall not--shan't [FB:nt]
will not---won't [wEunt]
can not-can't [kB:nt]
must not-mustn't [5mQsnt]
should not-- shouldn't
would not-- wouldn't
could not-- couldn't
dare not- daren't [dZEnt]
need not-- needn't
在疑问句中的用法
情态动词在疑问句中的用法和助动词相同。如：
May I ask you a question? 我可以问你一个问题吗?
Can you let me use your dictionary for a minute? 你能把字典借我用一会儿吗?
Would you like to visit the heavy machinery plant? 你想参观重型机器厂吗?
注意have to在疑问句中的位置。如：
Do you have to go out today? 你今天一定得出去吗?
Does he have to finish the work tomorrow? 他明天非做完这项工作不可吗?
基本概念
（一）情态动词的定义
情态动词表示说话人对某一动作或状态的态度。
（二）情态动词的特点
1）有一定词义；2）不受主语人称和数的变化影响；3）与主要动词的原形（或称不带to的不定式）一起构成谓语（除ought to作固定词组看待）。
（三）情态动词的分类和意义 意义 情态动词
can may might could would will
shall must should ought
to used to
可能性 *** *** *** **
能力 ** **
许可 ** * * *
习惯 **
意志或意愿 * ** ** **
预见或将来 ** *** ***
虚拟 * *** ***
义务或职责 强
弱
***
*** ***
推断 强
弱
***
** *** ***
过去的状态或习惯 ***
注：表中***表示主要用法；**表示次要用法；*表示不通常用法。
（四）情态动词的基本用法
1. can (could)
1）表示能力，could主要指过去时间。
Two eyes can see more than one. 两只眼比一只眼看得清。
Could the girl read before she went to school? 这女孩上学前能识字吗？
2）表示可能（理论上或是逻辑判断上）。
The temperature can fall to –60℃, that is 60℃ below freezing.
气温可降至-60℃，也就是零下60℃。
He cant (couldnt) have enough money for a new car. 他不可能有足够的钱买新车。
You mustnt smoke while youre walking around in the wood. You could start a fire.
在林子里走时勿吸烟，那样可能会引起火灾。
3）表示允许。
Can I have a look at your new pen? 我可以看一看你的新钢笔吗？
He asked whether he could take the book out of the reading-room.
他问他可不可以把书带出阅览室。
4）表惊异、怀疑、不相信等态度。主要用于否定句、疑问句或感叹句中。
Where can (could) they have gone to? 他们会去哪儿了呢？
He cant (couldnt) be over sixty. 他不可能超过六十岁。
How can you be so careless? 你怎么这么粗心？
5）比较委婉客气地提出问题或陈述看法。
Can (Could) you lend me a hand? 帮我一把好吗？
Im afraid we couldnt give you an answer today. 恐怕我们今天不能给你答复。
2. may (might)
1）表允许，might可以指过去时间，也可指现在时间，语气更委婉。
You may take whatever you like. 你喜欢什么就拿什么。
He told me that I might smoke in the room. 他告诉我可以在房间里抽烟。
May (Might) I ask for a photo of your baby? 我可以要一张你宝宝的照片吗？
在回答以may引起的问句时，多避免用这个词，而用其它方式，如Yes, please. / Certainly.
/ Please dont ./ Youd better not. / No, you mustnt.等，以免显得太严峻或不客气。
2）表可能（事实上）。可以指过去时间，也可以指现在时间，但语气更加不肯定。
He may be at home. 他可能在家。
She may not know about it. 她可能不知道这件事。
He was afraid they might not agree with him. 他担心他们可能不同意他的意见。
They might be having a meeting, but Im not sure. 他们有可能在开会，不过我不肯定。
3. must
1）表示义务。意为“必须”（主观意志）。
We must do everything step by step. 我们一切都必须循序渐进地做。
You mustnt talk to her like that. 你不可能那样对她说话。
--Must we hand in our exercise-books now? 我们现在就要交练习本吗？
--No, you neednt. / No, you dont have to. 不必。（这种情况下，一般不用mustnt）
2）表示揣测。意为“想必、准是、一定”等，只用于肯定句。
He must be ill. He looks so pale. 他准是病了。他的脸色苍白。
Shes wearing a diamond necklace. She must have a lot of money. 她戴着钻石项链，一定很有钱。
4. shall
1）表征询意见，用于第一、第三人称疑问句。
Shall I get you some tea? 我给你点茶好吗？
Shall the boy wait outside? 让那男孩在外面等吗？
What shall we do this evening? 我们今晚做什么？
2）表说话人的意愿，有“命令、允诺、警告、决心”等意思，用于第二、第三人称陈述句。
You shall do as I say. 按我说的做。（命令）
You shall have my answer tomorrow. 你明天可以得到我的答复。（允诺）
He shall be sorry for it one day, I tell you. 有一天他会后悔的，我告诉你。（警告）
Nothing shall stop us from carrying out the plan. 什么也不能阻止我们执行这项计划。（决心）
5. will
1）表意愿，用于各种人称陈述句。
I will do anything for you. 我愿为你做任何事。
None is so blind as those who wont see. 不愿看的人眼最瞎。
If you will read the book, Ill lend it to you. 如果你愿意读这本书，我会把它借给你。
2）表请求，用于疑问句。
Will you close the window? Its a bit cold. 请你把窗户关上好吗？有点冷。
Wont you drink some more coffee? 再来一点咖啡好吗？
3）表示某种倾向或习惯性动作。
Fish will die out of water. 鱼离开水就不能活。
The door wont open. 这门打不开。
The boy will sit there hour after hour looking at the traffic go by.
那男孩常常坐在那里好几个钟点，看着车辆行人通过。
6. should
1）表义务。意为“应该”（某件事宜于做），用于各种人称。
You should be polite to your teachers. 你对老师应该有礼貌。
You shouldnt waste any time. 你不应该浪费时间。
2）表推测，意为“想必一定、照说应该、估计”等。
The film should be very good as it is starring first-class actors.
这部新电影是一流演员主演的，估计拍得很好。
They should be home by now. 照说他们现在应当已经到家了。
7.would
1）表意愿。
They would not let him in because he was poorly dressed. 他们不让他进去因为他衣着破旧。
I said I would do anything for you. 我说过我愿意为你做任何事。
2）表委婉地提出请求、建议或看法。
Would you like another glass of beer? 再来杯啤酒好吗？
Would you mind cleaning the window? 请把窗户擦一下好吗？
They wouldnt have anything against it. 他们不会有什么反对意见。
3）表过去反复发生的动作或过去的一种倾向。
Every time she was in trouble, she would go to him for help.
她每遇到麻烦都会向她求助。他告诉我盒子打不开了。
8. ought to
1）表义务，意为“应该”（因责任、义务等该做），口气比should稍重。
You are his father. You ought to take care of him. 你是他父亲，应当管他。
You oughtnt to smoke so much. 你不应该抽这么多烟。
2）表推测，暗含很大的可能，语气较弱。
Han Mei ought to know his telephone number. 韩梅该知道他的电话号码。
Theres a fine sunset; it ought to be a fine day tomorrow. 今天有晚霞，明天应该是个好天。
9. used to
表示过去的习惯动作或状态，现在不复发生或存在。疑问式和否定式有两种。
He used to live in the countryside, but now he lives in the city.他过去住在乡下，现在住在城里。
There used to be a building at the street corner, but it has been pulled down.
街道拐角处过去有座楼房，现在拆了。
I usednt (didnt use) to smoke. 我过去不抽烟。
Used you (Did you use) to go to school on foot? 你过去常步行去学校吗？
重点疑难
（一）need和dare的用法
need和dare既可用作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句和疑问句。用作实义动词时，可用于各种句式。
1.用作情态动词
--Need I come? --Yes, you must. --我需要来吗？ --需要。
You neednt telephone him now. 你现在不必打电话给他。
I dont think you need worry. 我想你不必发愁。
She dare not go out alone at night. 她晚上不敢一个人出去。
How dare you say Im unfair? 你竟敢说我不公平？
Not one of them dared mention this. 他们谁也不敢提这件事。
2.用作实义动词
You dont need to do it yourself. 你不必亲自做这件事。
We need to tell them the news. 我们需要把这消息告诉他们。
The table needs painting (to be painted.). 桌子需要油漆一下。
We should dare to give our own opinion. 我们要敢于提出自己的观点。
He did not dare (to) look up. 他不敢抬头看。
I dare day hell come again. 我想他会再来的。
（cI dare say…为固定习语）
（二）情态动词后跟完成式和进行式的用法
1.情态动词后跟完成式，表“应当已经……”，“想必已经……”，“本来可以……”等意。
I should have finished the work earlier. 我应当早一点完成这项工作的。
He isnt here. He must have missed the train. 他还未到，一定是没赶上火车。
Where can (could) he have gone? 他能到那里去了呢？
You may (might) have read about it. 你可能在报上已经读到这件事了。
You could (might) have been more careful. 你本来可以更细心的。
He neednt have worried about it. 他本不必为此事担心。
There was a lot of fun at yesterdays party. You ought to have come, but why didnt you?
昨天的聚会非常有意思。你本应该来，为何不来呢？
2. 情态动词后跟进行式，表示“想必正在……”，“可能正在……”，“应当正在”等意。
Its twelve oclock. They must be having lunch. 现在是十二点。他们一定正在吃饭。
They may be discussing this problem. 他们可能正在论讨这个问题。
He cant be telling the truth. 他说的不可能是真话。
She shouldnt be working like that. Shes still so weak. 她不应当那样干，她身体仍那么虚。
（三）几组词的辨异
1. can 和be able to
1）情态动词can只有两种时态形式，现在式can和过去式could，而be able to有多种时态形式。
Mary can play the piano. She has been able to play it since she was 5.
玛丽会弹钢琴。她五岁起就会弹了。
2）用在过去时中，could经常表示能够做某事，事实上不一定去做，而was∕were able to则表示“过去做成了某事”。在否定句中两者可通用。
He could swim across the English Channel. But he didnt feel like it that day.
他能游过英吉利海峡，但那天他不想游。
Yesterday I was able to get home before the heavy rain. 昨天我在下大雨前赶到了家里。
2. must和 have to
must表示主观意志，而have to表示由于客观因素不得不做某事。must没有过去式，除在间接引语中可用于表示过去时间，在直接引语中表示过去时间应该用had to代替。
I told her that she must give up smoking. 我叫她必须戒烟。
We had to get everything ready that night. 我们那晚得把一切准备就绪。
3. would和used to
1）used to表示过去与现在或过去某时与后来的情况有不同，而would只表过去的情况。
People used to think that the earth was flat.
过去人们认为地球是平的。（现在人们不这么认为。）
She would go out for a walk in the morning when she was in the country.
在乡下时，她总是在早晨去散会儿步。（可能现在仍有散步的习惯。）
2）used to可表示过去的习惯动作和经常的情况，而would只表示过去的习惯动作。
He used to ∕would smoke while writing. 过去他写东西时常抽烟。
She used to be fat. 她过去很胖
专项练习
1. I __________ you, because I thought I must be wrong.
A. dare not ask B. dare not to ask C. dare not asking D. dare to not ask
2. There __________ some flowers in the garden.
A. were used to be B. used to be C. uses to be D. used to be having
3. “__________ I take it out?” “Im sorry, you __________.”
A. Could …couldnt B. Might…might not C. Could…can D. May…cant
4. You were stupid to climb the tree. You __________ hurt yourself.
A. may B. might C. will D. might have
5. You __________ those letters. Why didnt you ?
A. should post B. should have posted C. must have posted D. ought to post.
6. All the lights are on, the Smiths __________ up.
A. must get B. is getting C. must be getting D. would get
7. He __________ lead a horse to the water but he __________ not make it drink.
A. will…can B. may…can C. may…dares D. dare…can
8. “Need we do this job now?” “Yes, __________.”
A. you need B. you should C. you must D. you can
9. __________ to have lunch with us today?
A. Do you likes B. Would you like C. Will you liked D. Have you liked
10. He said that you __________ watch TV all the evening if you wished.
A. may B. must C. can D. might
11. –Is John coming by train? --He should, but he __________ not. He likes driving his car.
A. must B. can C. need D. may
12. Peter __________ come with us tonight, but he isnt very sure yet.
A. must B. can C. may D. will
13. Michael __________ be a policeman, for hes much too short.
A. neednt B. cant C. shouldnt D. wont
14. I thought you __________ be hungry, so I have brought you some cakes.
A. may B. might C. can D. could
15. I wonder how he __________ that to the teacher.
A. dare to say B. dare saying C. not dare say D. dared say
16. Come on! We __________ hurry because there isnt much time left.
A. may B. must C. can D. need
17. Amy did best in the English test. She __________ hard last week.
A. must have working B. should have worked C. should work D. must work
18. The fire spread through the hotel very quickly but everyone __________ get out.
A. had to B. would C. could D. was able to
19. –--I stayed at a hotel while in New York. ---Oh, did you? You __________ with Barbara.
A. could have stayed B. could stay C. would stay D. must have stayed
20. Its nearly seven oclock. Jack __________ be here at any moment.
A. must B. need C. should D. can
答案：
1.A2.B3.D4.D5.B6.C7.B8.C9.B10.D11.D12.C13.B14.B15.D16.B17.A18.D19.A20.
1)表过去的可能和许可，(多用于间接引语中)
At that time we thought the story could not be true.
那时我们认为所说的事不可能是真的。
Father said I could swim in the river.
爸爸说我可以在河里游泳。
2)表过去的能力
I could swim when I was only six.
我刚六岁就能游泳。
Could在肯定句中表示过去的能力时，常表抽象的一般的能力。
He could be very naughty when he was a child.
他小时候会是很顽皮的。
3)表“允许”。可表示委婉客气的提出问题或陈述看法
Could I use your bike?
Yes, you can.
他会记得那时吗?
I’m afraid I couldn’t give you an answer today.
恐怕我今天不能回答你。
The teacher said you could go to the store for sweets.
老师说你可以去商店买糖。
3)Could/can+have done 结构表示对过去发生的事情的“怀疑”或“不肯定”。 could 加完成式还用于肯定句时一般表过去可能完成而却未完成的动作。
Can they have won the basketball match?
他们赢了那场篮球赛吗?
What you referred to just now can have made her very sad.
你刚刚所谈到的可能令他很伤心。
You could have completed the task a little earlier.
你本来能早点完成任务的。(但事实上并没有提前完成任务)
I could have passed my examination easily but I made too many stupid mistakes.
我本可以轻易通过考试，但我犯了太多不该犯的错误。
如表具体做某一件事的能力时，则须用 be able to .
He was able to translate the article without a dictionary.
他可以不用词典翻译那篇文章。
Can表示一贯的能力 ，be able to表示客观能力和通过努力可以达到的能力
I can’t swim. But I am sure I will be able to swim through more practicing.
The fire spread through the hotel, but everyone was able to get out
When the boat sank he was able to swim to the bank
1)表示请求、可以、允许。
You may drive the tractor. 你可以开那台拖拉机。
2)当回答由may 引起的问题时，否定答语要用must not,表示“不许可”、“不应该”、“不行”。
May I come in?
Yes, you may.
No,you can’t
No, you may not .
No ,you mustn’t
No ,you’d better not.
3) may /might 推测性用法 可能
He may be right.
He may not come today (可能不)
He may /might come tomorrow.
, 注意: 1只用于肯定和否定句中,不用于疑问句中。
2 might 比may可能性更小
He might get a job.
He may get a job.
3 may no 可能不 can not不可能
He may not come
He can’t come
3)表建议(可和as well 连用)
You may(might)as well stay where you are.
你还是原地待着好。(may as well 有“还是……的好”的含义)
4)表祝愿
May you be happy!
1)表示必须、必要
We must do everything step by step .我们必须按部就班地做一切事情。
Why must you always bother me? 为什么你偏要打扰我呢。
2)must be + 表语的结构，通常表示猜测，含有“一定”之意。(只用在肯定句中)
He must be an honest boy. 他一定是个诚实的男孩。
This must be your room. 这一定是你的房间。
3)must 的否定式有两个：当回答由must引起的问题时，否定答复要用needn’t或don’t have to 表示“不必”、“无须”、“用不着”、“不一定”的意义。当表示“不应该”、“不许可”、“禁止”时，就用must not。
Must I go tomorrow?明天我必须去吗?
Yes, please.是的，请吧!
No , you needn’t. 不，你不必去。
4)must +have +过去分词的结构，常用在肯定句中，表示对过去发生行为的推测，含有“一定”、“准是”的意思。否定和疑问句用can。
She must have studied English before.她以前一定学过英语。
★ 语法-动词不定式
