何學(xué)群
一概述
1. 英語(yǔ)中助動(dòng)詞主要有兩類(lèi)：一是基本助動(dòng)詞，如have, do, be；二是情態(tài)助動(dòng)詞。
2. 情態(tài)動(dòng)詞與其他動(dòng)詞連用表示說(shuō)話人的語(yǔ)氣。情態(tài)動(dòng)詞可表達(dá)建議、要求、可能和意愿等。
3. 情態(tài)動(dòng)詞沒(méi)有人稱和數(shù)的變化。
4. 情態(tài)動(dòng)詞的用法可分為4個(gè)大類(lèi)：本義，規(guī)勸，推測(cè)，和責(zé)備（虛擬）用法
二 本義
A. 常用詞：
1. may
1)表示請(qǐng)求、可以、允許; 否定答語(yǔ)要用must not,表示“不許可”、“不應(yīng)該”、“不行”。
You may drive the tractor. 你可以開(kāi)那臺(tái)拖拉機(jī)。
May I come in? Yes, you may. No, you can’t (mustn’t, you’d better not.)
May I / we …？肯定回答: Yes, please/Certainly； Please don’t/No, you mustn’t.
“May we leave now?” “No, you mustn’t. You haven’t finished your home work yet.”
Might I trouble you for a light? “You may indeed.” “我可以向你借火嗎？”“當(dāng)然可以”
回答一般是 sure, certainly, of course,不能用might
2) 表祝愿 May you be happy! May you succeed！祝你成功！
2. must
1) 表示說(shuō)話人的意志和義務(wù)。或要求對(duì)方必須作某事。
We must do everything step by step .我們必須按部就班地做一切事情。
You must be there on time. 你務(wù)必要按時(shí)到達(dá)那里。
2) 語(yǔ)氣，“偏偏”
Why must you always bother me? 為什么你偏要打擾我呢。
3）must 的否定式：needn’t, don’t have to “不必”、“無(wú)須”、“用不著”、“不一定”。
must not “不應(yīng)該”、“不許可”、“禁止”
--- Must I go tomorrow?明天我必須去嗎？
--- Yes, please.是的, 請(qǐng)吧！No , you needn’t. 不，你不必去。
3 Shall
1）用于一、三人稱疑問(wèn)句、表征求對(duì)方意見(jiàn)或向?qū)Ψ秸?qǐng)求。
-Shall he come in? - Come in, please. -可以讓他進(jìn)來(lái)嗎？-請(qǐng)進(jìn)。
What shall I wear on the journey? 我路上穿什么好呢？
Shall we dance? 我們跳舞好嗎？
Shall he come to see you? 要不要他來(lái)看你？
2）用于二、三人稱，表示保證、承諾、威脅、警告。
You shall be punished if you insist on doing it this way. 如果你堅(jiān)持這樣做就會(huì)受到懲罰。
If he passes the exam he shall have a holiday.
The law shall come into effect on May 1st.
注： 用于第一人稱表將來(lái)，理解為助動(dòng)詞用法
I shall go to work after I have finished school. 畢業(yè)后，我會(huì)去工作。
4. should
1)表達(dá)說(shuō)話人的感情如驚奇、憤怒、失望、竟然等，常用在why , how開(kāi)頭的疑問(wèn)句中或that 引導(dǎo)的從句中
Why should you be so late? 為什么你竟這么晚？
How should I know?我怎么會(huì)知道？
I'm sorry that you should think so badly of me. 你竟把我想得那么壞，我感到遺憾。
You can’t imagine that a well-behaved gentleman should be so rude to a lady.
你不能想象行為端正的男士會(huì)對(duì)一個(gè)女士如此粗魯。
I didn’t expect that he should have behaved like that. 我無(wú)法想象他竟然這樣做。
I am sorry that she should be so careless. 我感到遺憾她竟會(huì)那樣粗心。
2)一般不應(yīng)被認(rèn)為是情態(tài)動(dòng)詞shall的過(guò)去式，主要用法有：
A. 用于第一人稱疑問(wèn)句中詢問(wèn)對(duì)方的意愿，但語(yǔ)氣較委婉溫和，如：
What should we do now? 我們現(xiàn)在該怎么辦？
B. 表示應(yīng)該、必須，常與must 換用。例如：
We should (must) master a foreign language at least. 我們應(yīng)當(dāng)至少掌握一門(mén)外語(yǔ)。
It is suggested that he should go there by air. 建議他乘飛機(jī)去那里。
5. need
考試中主要測(cè)試 need 作情態(tài)動(dòng)詞與作實(shí)義動(dòng)詞的區(qū)別，need 作情態(tài)動(dòng)詞時(shí)，后面跟動(dòng)詞原形，即 “need do”。通常用在疑問(wèn)句和否定句中，表示詢問(wèn)是否有“必要”，其否定形式為needn’t，表示“不必”；疑問(wèn)形式為 Need … do? 極少用于肯定句。
1）I don’t think we need turn the light on at that time.
2）Need you ride a bike to school?
6. will
1) will作情態(tài)動(dòng)詞，表示意愿、習(xí)慣等。
It will be highly appreciated if you will send us your latest price list.
Boys will be boys. 男孩子究竟是男孩子。
No matter what you say, he will always argue with you. 不管你說(shuō)什么，他總是和你爭(zhēng)論。
A wise man changes his mind, a fool never will. 聰明人能隨機(jī)應(yīng)變，傻瓜是不會(huì)的。
2) 用于第二人稱作主語(yǔ)的疑問(wèn)句中，表示對(duì)對(duì)方的請(qǐng)求，would的語(yǔ)氣比will委碗
Would/will you kindly tell me the way to the station? 請(qǐng)問(wèn)到火車(chē)站怎么走？
Will/would you please do...,Would you like to do...,Would you mind doing...都表示建議、詢問(wèn)、請(qǐng)求
Will you please pass me a cup of tea? Would you like me to give you a hand?
This box is too heavy, ____give me a hand? (CET-4 1998,1)
A) would you mind B) would you please C) will you like to D) will you please to
3）表示意志，決心或愿望。例如：
Surely we will support all the people in the world in their struggle for peace.
我們一定要支持全世界人民爭(zhēng)取和平的斗爭(zhēng)。
He would not let me try it . 他不肯讓我去試。
4）will表示經(jīng)常性、習(xí)慣性、傾向性，would表示過(guò)去的習(xí)慣行為。
He will sit there hour after hour looking at the traffic go by.
他會(huì)經(jīng)常一連幾個(gè)小時(shí)坐在那兒觀看來(lái)往的車(chē)輛。
Water will boil at 100℃. 水在攝氏100度時(shí)總是要沸騰的。
He would come to see me when he was in Beijing. 他在北京時(shí)，常來(lái)看望我。
On Sundays he would get up early and go fishing.
7. can (could) 表能力;
1) can表能力時(shí)意味著憑體力或腦力或技術(shù)等可以無(wú)甚阻力地去做某事。
I can climb this pole. 我能爬這根桿子。 Fire can’t destroy gold. 火燒不毀金子。
He is only four , but he can read. 他只有4歲，但已認(rèn)得字了。
I could swim when I was only six. 我剛六歲就能游泳。
2) 允許（和may意思相近，委婉語(yǔ)氣could）
Can (May) I come in ? 我能進(jìn)來(lái)嗎？Can I smoke here ? 我可以在這里抽煙嗎？
Could I give you dinner one of these days? 這幾天我請(qǐng)你吃頓飯行嗎？
回答: yes, please; Yes, of course you can.
No, you mustn't /cannot/ may not 不用could
8. ought to
Ought to 后接動(dòng)詞原形，表義務(wù)，但不及must 那樣具有信心，如：
You don’t look well. You ought to go to see the doctor. 你氣色不好，應(yīng)該去看病。
Ought to 用于否定句，其否定形式可縮略為oughtn’t ，如：
You oughtn’t to smoke so much. 你不應(yīng)該抽這么多煙。
也可以用于疑問(wèn)句： Ought you to smoke so much?你應(yīng)該抽這樣多煙嗎？
Ought to 在間接引語(yǔ)中表過(guò)去時(shí)形式不變：
He said you ought to tell the police. 他說(shuō)你應(yīng)該去報(bào)告警察。
B. 要注意的幾對(duì)詞
1. can 和 be able to
1) can 與 be able to表示能力：can (could)表示主觀能力，不表示意愿，
My grandma is over seventy, but she can still read without glasses.
He is able to give up his bad habits.
2) Can表示一貫的能力 ，be able to表示客觀能力和通過(guò)努力可以達(dá)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
3)表示將來(lái)式時(shí)，表具體做某一件事的能力時(shí)，則須用 be able to
You will be able to skate after you have practiced it two or three times.你練習(xí)兩三次后就會(huì)溜冰了。
He was able to translate the article without a dictionary. 他可以不用詞典翻譯那篇文章。
2. must 和 have to “必須”
（1）must 強(qiáng)調(diào)“內(nèi)在的職責(zé)”、“義務(wù)”，而have to 強(qiáng)調(diào)“外界壓力”、“不得已而為之”。
You must come to the classroom before eight.
It is raining hard outside, but I have to leave now.
I must clean the room.（主觀想法） I have to clean the room.（客觀需要）
（2）have to多種時(shí)態(tài)，must一般用于現(xiàn)在時(shí)，其過(guò)去時(shí)had to, 將來(lái)時(shí)shall / will have to.
We had to be there at ten .我們得在十點(diǎn)鐘到那里。
We will have to reconsider the whole thing. 這一切我們將不得不重新加以考慮。
（3） must否定回答，不用mustn’t，而用needn’t或don’t have to
“Must we do it now?” “No, you needn’t.”
3. Need 和dare： 考試中主要測(cè)試作情態(tài)動(dòng)詞和作實(shí)義動(dòng)詞的區(qū)別。
a. 有無(wú)助動(dòng)詞
b. 詞尾有無(wú)s(need 除外，因?yàn)橐话悴挥糜陉愂鼍?
⑴need 作情態(tài)動(dòng)詞，表示"需要"，只用于否定句和疑問(wèn)句中，無(wú)人稱和數(shù)的變化。
We needn't go there tomorrow. 我們不必明天去那里。
Need I tell you all the details? 我需要把一切詳情告訴你嗎？
⑵dare作情態(tài)動(dòng)詞，通常用在否定句和疑問(wèn)句中，無(wú)人稱和數(shù)的變化。
He dare not do so. 他不敢那么做。
I dare not stand on the chair. 我不敢站在椅子上。
How dare you say such a thing? 你怎么敢說(shuō)這種話？
⑶need作行為動(dòng)詞，與一般動(dòng)詞的變化相同, 后面接"to + 動(dòng)詞原形"。
Do I need to tell you all the details? 我需要把一切詳情告訴你嗎？
It needs to be done at once. 這件事需要馬上做。
You don't need to worry about that. 你不必為那事?lián)摹?/p>
You didn't need to come. 你當(dāng)時(shí)沒(méi)必要來(lái)。
dare 也可作行為動(dòng)詞, 用在肯定句中（I dare say除外）和疑問(wèn)句中，后面都接"to +動(dòng)詞原形"，在否定句中有時(shí)帶to, 有時(shí)不帶to, 如：
I dared to do so. 我敢于這樣做。
She dares to go out alone at night. 她晚上敢一人出去。
Did he dare to do so? 他敢這樣做嗎？
He did not dare (to ) do so. 他不敢這樣做。
⑷慣用語(yǔ)：I dare say 表示"我想"、"大概"。（dare say 也可以連寫(xiě)）
There's something wrong with the radio, I dare say. 收音機(jī)恐怕有點(diǎn)毛病。
I daresay you are right. 我想你是對(duì)的。
C. 用作情態(tài)動(dòng)詞的其他短語(yǔ): would rather, would sooner, would (just) as soon, had rather, had better, had sooner, can not but, may (just) as well
1）The soldier would sooner die than surrender(投降).
2）The brave soldier would as soon die as yield（屈服）to such an enemy.
3）I’d rather walk than take a bus.
4）If you don’t like to swim, you may just as well stay at home.
注：這些短語(yǔ)后一般直接跟動(dòng)詞原形.
would (had) rather, would (had) sooner, would (just) as soon后可跟that從句，that 常省去，從句要用虛擬語(yǔ)氣。對(duì)現(xiàn)在和將來(lái)的假設(shè)用過(guò)去時(shí)，對(duì)過(guò)去的假設(shè)用過(guò)去完成時(shí)。例如：
1）I would rather you came on Sunday.
2）I would sooner you hadn’t asked me to speak yesterday.
二 規(guī)勸
1. 肯定：may(might), may/might (just) as well ,should,
2. 否定：may not, cannot, must not
You can not smoke in the bus. 公共汽車(chē)上不許吸煙。
Can't you do it tomorrow? 你不能明天做嗎？
Students may not stay out after midnight. 學(xué)生午夜后不得在外逗留。
You mustn't play football in the street, children. 孩子們，不準(zhǔn)在馬路上踢球。
3. 有些短語(yǔ)：
may/might (just) as well “不妨，最好”，與had better相近；
Since the flight was cancelled, you might as well go by train.
既然航班已經(jīng)取消了，你不妨乘火車(chē)吧。相當(dāng)于you had better go by train。
cannot / can’t…too …“越……越好，怎么也不過(guò)分”。變體：cannot…over…
You cannot be too careful when you drive a car.駕車(chē)時(shí)候，越小心越好。
The final chapter covers organizational change and development. This subject cannot be over emphasized.
三 推測(cè)：
一）．搞清楚兩條線索：
1．意義上分為肯定的推測(cè)和否定的推測(cè)兩種；
must , will, should, may, might , could表示可能性依次減��；
can’t, couldn’t, may not, might not不可能性依次減小
“I wonder how Tom knew about your past.” “He must / could / may / might have heard of it from Mary.”
He must tell a lie. 他肯定是說(shuō)謊。Can he tell a lie? 他會(huì)說(shuō)謊嗎？He can’t tell a lie. 他不會(huì)說(shuō)謊的。
Since the ditch is full of water, it must have rained last night.
You couldn’t have met my grandmother. She died before you were born.
Could /Can it have happened last night ? 它在昨晚發(fā)生了嗎？
It may rain tomorrow. 明天可能下雨。 (I'm told by the radio.)
What you said might be true. 你說(shuō)的可能對(duì)。
She may be staying at home.
Anybody can make mistake.任何人都可能犯錯(cuò)誤。
The weather here could be very cold in winter. 冬天這的天氣有時(shí)很冷。
2 時(shí)間上分為現(xiàn)在，將來(lái)和過(guò)去
A) 現(xiàn)在：(一般情況和強(qiáng)調(diào)推測(cè)正在進(jìn)行) (must be; must do; must be doing)
Can it be true? 這會(huì)是真的嗎？
He must be playing basketball in the room.
B）過(guò)去：（一般情況和強(qiáng)調(diào)推測(cè)過(guò)去正在進(jìn)行）(must have done; must have been doing)
“The dictionary has disappeared. Who could have taken it?”
“Tom could have taken it. He was alone yesterday.”
I can’t find my keys. I may / might have left them at the school yesterday.
What you referred to just now can have made her very sad. 你剛剛所談到的可能令他很傷心。
He might not have settled the question. 他可能尚未解決那個(gè)問(wèn)題。
She must have studied English before.她以前一定學(xué)過(guò)英語(yǔ)。
They should have been meeting to discuss the problem.
He may / might have been buying stamps in the post office when you saw him.
They are sweating all over. They must have been working in the fields.
They may have been discussing the problem this morning.
She couldn’t have been swimming all day.
Can they have won the basketball match？他們贏了那場(chǎng)籃球賽嗎？
C）將來(lái)：參見(jiàn)下面具體的情態(tài)動(dòng)詞 (形式同現(xiàn)在)
注意：適當(dāng)考慮時(shí)態(tài)變化 could, might等大多應(yīng)認(rèn)為是語(yǔ)氣較弱。
Electric irons could be dangerous; they might give you a severe shock. 電熨斗會(huì)有危險(xiǎn), 可能電著人。
二） 其他具體的可能性：
1． can多用于否定與疑問(wèn)結(jié)構(gòu)中，但也可用在肯定句中,表示潛在的或理論上的可能性
Can the news be true? 這消息可能是真的嗎？
It can’t be true. 它不可能是真的。
What can he possibly mean? 他可能是什么意思？
A house in the center of London can cost a lot of money.
Attending the ball can be very exciting.
The road can be blocked. 這條路可能會(huì)不通的。
may, might表示事實(shí)上的可能性。
The road may be blocked. 這條路可能不通了。
He may have done the work last night, didn’t he?
She may be staying at home.
對(duì)比：
The railways may be improved. =It is possible that the railways will be improved.
=Perhaps/Maybe/Possibly the railways will be improved.
鐵路可能會(huì)得到改進(jìn)。（意味著已有具體的改進(jìn)計(jì)劃或方案。）
The railways can be improved.=It is possible for the railways to be improved.
鐵路可以得到改進(jìn)。（意思是鐵路還不完善，尚有問(wèn)題存在。）
He looks pale. He may be ill.他臉色蒼白，可能有病。
He is in poor health. He can be ill at any time.他體質(zhì)很差，任何時(shí)候都有可能生病。
2．will表示說(shuō)話人對(duì)將來(lái)和現(xiàn)在的預(yù)測(cè)，表示某種傾向和習(xí)慣性,尤其指在某個(gè)條件下。
I think he will be all right now. 我想他現(xiàn)在一定好了。
That would be his mother. 那肯定是他母親。
Oil will float on water. 油浮在水面上。
He'll talk for hours if you give the chance. 如果給他機(jī)會(huì)，他會(huì)談上幾個(gè)小時(shí)。
3. must只用在肯定句中
He must be an honest boy. 他一定是個(gè)誠(chéng)實(shí)的男孩。
He must have finished the work, hasn’t he?
He must be playing basketball in the room.
4. should (ought to)
表示很可能、預(yù)期的意思，指一種嘗試性推論，是must的語(yǔ)氣較弱的對(duì)應(yīng)詞，”應(yīng)該會(huì)、一定---吧”。比較：Our guests must be home by now.(‘I am certain’)我們的客人現(xiàn)在一定到家了。
（根據(jù)他們動(dòng)身的時(shí)間、路程遠(yuǎn)近、速度等具體條件，我能斷定/肯定他們現(xiàn)在已經(jīng)到家了。）
Our guests should(ought to) be home by now.(‘They probably are, but I’m not certain.)
我們的客人現(xiàn)在該到家了。（含義是我想他們很可能到家了，但我不能肯定”）
It's nearly seven o'clock.. Jack ____be here at any moment. (NMET95)
A .must B. need C. should D. can
三）表猜測(cè)語(yǔ)氣的反意疑問(wèn)句的構(gòu)成
He must be reading, isn’t he? 他肯定在讀書(shū)，不是嗎？
He must/may be in the room, isn’t he?
He can’t be in the room, is he？
You must do it yourself, don’t you? 你一定要自己做，不是嗎？
He must have gone over the article, hasn’t he? 他一定已經(jīng)檢查了這篇論文，不是嗎？
It must have rained last night, didn’t it? 昨晚一定下過(guò)雨了，不是嗎？
Mary ______my letter; otherwise she would have replied before now.
[A] couldn’t have received [B] ought to have received
[C] has received [D] shouldn’t have received
四 責(zé)備: (虛擬語(yǔ)氣)
1. 情態(tài)動(dòng)詞的選用考慮該詞的本義
2．同樣需要分清時(shí)間
A）現(xiàn)在：
You ought not to make fun of him. He is not the one you laugh at but learn from.
在“It is natural (strange, natural, necessary, surprised, impossible, important ) that……”句型中，
在lest（以免）、for fear (that) (以防)、in case（以備萬(wàn)一）等之后也要用should+動(dòng)詞原形;
在advise, sugest, order, demand, request 等的從句中;
謂語(yǔ)動(dòng)詞要用should +動(dòng)詞原形, 表示“理所當(dāng)然”、“奇怪”、“必要”、“驚異”等的意思。
It is necessary that he(should) be sent there at once. 有必要馬上派他到那里去。
It is strange that he should say so. 他會(huì)說(shuō)這樣的話真是奇怪。
Let us go at once lest we should be late for the train. 我們馬上走吧，以免趕不上火車(chē)。
B）過(guò)去：（情態(tài)動(dòng)詞+have done/been）
You should have come here five minutes earlier. 你應(yīng)該早來(lái)5分鐘的。
With all the work finished, I should have gone to the party last night.
You needn’t have waken me up; I don’t have to go to work today.
You needn’t have come over yourself.
I regret having left the work unfinished; I should have planned everything ahead carefully.
我本來(lái)應(yīng)該事先認(rèn)真地把每件事情規(guī)劃的很好，但實(shí)際上作者沒(méi)有規(guī)劃好，以至工作沒(méi)有完成。
What you said is right, but you could have phrased it more tactfully.
I should have thought of that. 這一點(diǎn)我是應(yīng)當(dāng)想到的。（但沒(méi)想到）
They should not have left so soon.他們不應(yīng)當(dāng)走得這么早。（但已走了）
You could have completed the task a little earlier. 你本來(lái)能早點(diǎn)完成任務(wù)的。
I could have passed my examination easily but I made too many stupid mistakes.
我本可以輕易通過(guò)考試，但我犯了太多不該犯的錯(cuò)誤。
例題：
As it turned out to be a small house party, we ______so formally.
[A] needn’t dress up [B]did not need have dressed up
[C] did not need dress up [D] needn’t have dressed up
C) 將來(lái)：常用在if 從句中，構(gòu)成虛擬語(yǔ)氣。
If it should/were to------, ____________________________.
If he should drop in, give him my message. 他如果來(lái)訪，就把我的條交給他。
= Should he drop in, give him my message.
Ask her to ring me up if you should see her. 你如若見(jiàn)到她，讓她給我打個(gè)電話。
If it should snow tomorrow , the meeting would be put off．如果明天下雪的話，運(yùn)動(dòng)會(huì)就會(huì)推遲。
Should it blow hard，we would not go out for a picnic．萬(wàn)一明天刮大風(fēng)，我們就無(wú)法去野餐了。
五 注意點(diǎn)
1．當(dāng)試題的前句和后句在動(dòng)作和意義上相互補(bǔ)充說(shuō)明，且整個(gè)句意在動(dòng)作和時(shí)間上是一個(gè)整體時(shí)，我們可用“統(tǒng)一”關(guān)系來(lái)解決這樣的試題。常見(jiàn)的結(jié)構(gòu)有：
must have done： 表示對(duì)過(guò)去動(dòng)作的肯定推測(cè)，常譯作“一定做了……”，只能用于肯定句中。
can’t／couldn’t have done牱穸ㄐ問(wèn)
Can／Could...have done﹖ 疑問(wèn)式
could ／might have done：表示對(duì)過(guò)去發(fā)生的動(dòng)作的可能性推測(cè)，常譯作“可能做了……”。
例題：
1) Sorry I’m late．I ____have turned off the alarm clock and gone back to sleep again(北京 2000春)
A． might B． should C． can D． will
該題前句說(shuō)明了結(jié)果，后句接著說(shuō)出了產(chǎn)生這種結(jié)果的可能性，對(duì)前句進(jìn)行補(bǔ)充說(shuō)明。
2) My sister met him at the Grand Theater yesterday afternoon, so he ____ your lecture．(上海 2000)
A. couldn’t have attended B. needn’t have attended
C. mustn’t have attended D. shouldn’t have attended
該題前句敘說(shuō)一個(gè)客觀事實(shí)，后句對(duì)前句進(jìn)行補(bǔ)充說(shuō)明，分析選項(xiàng)可知C是錯(cuò)誤的
3) Jack ＿＿＿＿ yet, otherwise he would have telephoned me． (上�！�97)
A. mustn’t have arrived B. shouldn’t have arrived
C. can’t have arrived D. need not have arrived
2．當(dāng)試題的前后句在動(dòng)作和意義上構(gòu)成轉(zhuǎn)折關(guān)系時(shí)，常借助“but, however, instead”等詞來(lái)表示過(guò)去的動(dòng)作與客觀事實(shí)不符，這時(shí)我們就可以用“對(duì)立”關(guān)系來(lái)解決這樣的試題。常見(jiàn)的有：
should have done /ought to have done：表示過(guò)去本應(yīng)該做某事而實(shí)際上沒(méi)有做。
should not have done /ought not to have done：表示過(guò)去本不應(yīng)該做某事但事實(shí)上卻做了。
need have done：表示過(guò)去本來(lái)有必要去做某事，但事實(shí)上沒(méi)有做。
need not have done：表示過(guò)去本來(lái)沒(méi)有必要做某事，但事實(shí)上卻做了。
4) I was really anxious about you． You ______ home without a word． (NMET2001)
A. mustn’t leave B. shouldn’t have left C. couldn’t have left D. needn’t leave
分析該題前后句之間的關(guān)系和語(yǔ)氣可知，事實(shí)上是“本不應(yīng)該離家出走卻走了”
5) I told Sally how to get here, but perhaps I ______ for her． (NMET’94)
A. had to write it out B. must have written it out
C. should have written it out D. ought to write it out
由句中的連詞but可知前后句之間是對(duì)立關(guān)系
3. 容易混淆的形式：
1）should have done: 推測(cè)和責(zé)備
---I sent him a letter last Monday.
---Really? So I guess he _____ it by now.
A. should receive B. should have received C. will receive D. could receive
六 總結(jié)
一、考查情態(tài)動(dòng)詞的基本用法
一些常見(jiàn)情態(tài)動(dòng)詞的非常用意義往往為高考考查的焦點(diǎn)，考生須確切理解其含義并根據(jù)句子意思選擇正確的情態(tài)動(dòng)詞。
例1：“The interest ______be divided into five parts, according to the agreement made by both sides.” declared the judge. (2004重慶)
A. may B. should C. must D. shall
例2：- The room is so dirty. ______ we clean it?
- Of course. (2003北京春)
A. Will B. Shall C. Would D. Do
分析：上述兩題均考查 shall的非常用含義，當(dāng)shall用于一、三人稱疑問(wèn)句中時(shí)，表示征求對(duì)方意見(jiàn)；用于二、三人稱陳述句中，表示說(shuō)話人給對(duì)方的命令、警告、允諾或威脅等。
例3：He’s strange -- he ____ sit for hours without saying anything.
A. shall B. will C. can D. must
分析：will用來(lái)談習(xí)慣和特性，尤其是不受時(shí)限必然發(fā)生的情況。本句意思為“他很怪，能一坐幾個(gè)小時(shí)一句話也不說(shuō)”。
例4：John, look at the time. _______ you play the piano at such a late hour？(2005全國(guó)Ⅲ)
A. Must B. Can C. May D. Need
例5：Tom, you _____leave all your clothes on the floor like this！(2005全國(guó)II)
A. wouldn’t B. mustn’t C. needn’t D. may not
分析：must用于疑問(wèn)句，表示責(zé)備、抱怨的感情色彩，意思為“偏要，硬要、干嘛”；而mustn’t則表示禁止、不允許，是說(shuō)話人強(qiáng)有力的勸告。
例6：You can’t imagine that a well-behaved gentleman _____ be so rude to a lady. (2001上海)
A. might B. need C. should D. would
分析：在某些名詞性從句中，should 表示驚異、意外等情緒，常譯為“竟然”。
如：It seems unfair that this should happen to me. 真不公平，這件事竟然發(fā)生在我身上。
例7：_____it rain tomorrow, the meeting would be put off.
A. Should B. Would C. Could D. Must
分析：在條件狀語(yǔ)從句中，should 表示“萬(wàn)一”，即可表示不能實(shí)現(xiàn)的假設(shè)，又可表示可以實(shí)現(xiàn)的假設(shè)。該句意思為“萬(wàn)一明天下雨，會(huì)議就延期�！�
例8 -Is John coming by train﹖
-He should, but he ＿＿＿＿＿＿ not． He likes driving his car． (NMET2002)
A. must B. can C. need D. may
分析: mustn’t 表示“禁止、不準(zhǔn)”；cannot 表示“不可能”；need not 表示“不必要”；may not 表示“可能不”。
例9 -I hear you’ve got a set of valuable Australian coins．________ I have a look﹖
-Yes, certainly． (北京2002春) A． Do B． May C． Shall D．Should
分析: 這是在征求對(duì)方的許可，may表示“允許、可以”，語(yǔ)氣比較委婉 shall常用于第一、三人稱作主語(yǔ)的疑問(wèn)句中,表示征求對(duì)方意見(jiàn)和指示，如果此空用shall，則意為“要（我）看一下嗎？”不符合上下文意思。
例10. I should have been there, but I ______ not find the time． (上海2000春)
A． would B．could C． might D． should
分析: 第二個(gè)分句表示過(guò)去的某種能力；C 項(xiàng)只表示語(yǔ)氣上的可能性，與題意不符。
例11. Johnny, you ______ play with the knife, you ______hurt yourself． (NMET’96)
A. won’t; can’t B. mustn’t; may C. shouldn’t; must D. can’t; shouldn’t
分析: mustn’t 表示“不可以；禁止”，分析題意可知第二個(gè)空表示某種可能性
例12 -Will you stay for lunch﹖
-Sorry, ______． My brother is coming to see me． (NMET’99)
A． I mustn’t B． I can’t C． I needn’t D． I won’t
分析: 因?yàn)椤拔业艿芤獊?lái)看我”，所以“不能留下”，因此對(duì)別人的邀請(qǐng)或要求應(yīng)給予禮貌的拒絕。A 項(xiàng)表示“禁止”；C項(xiàng)表示“不必要”；而D項(xiàng)表示“不會(huì)”，均不符合題意。
例13-Could I borrow your dictionary﹖
-Yes, of course you ＿＿＿＿＿．(MET’92)
A． might B． will C． can D. should
例14 --- When can I come for the photos﹖ I need them tomorrow afternoon．
--- They ______ be ready by 12:00． (NMET’98)
A. can B. should C. might D. need
例15 The fire spread through the hotel very quickly but everyone ______ get out．(NMET’97)
A. had to B. would C. could D. was able to
分析: 該題考查了could和be able to的區(qū)別，二者都可表示過(guò)去時(shí)間的能力，但如果表示過(guò)去成功地做了某事只能使用was /were able to do
例16 -Shall I tell John about it ﹖
-No, you _______． I’ve told him already． (NMET’94)
A. needn’t B. wouldn’t C. mustn’t D. shouldn’t
情態(tài)動(dòng)詞shall在試題中表示征詢對(duì)方意見(jiàn)或請(qǐng)求指示。答句暗示 “沒(méi)有必要了”
二、考查情態(tài)動(dòng)詞的推測(cè)用法
1、對(duì)現(xiàn)在或客觀事實(shí)的推測(cè)
對(duì)現(xiàn)在或客觀事實(shí)的肯定推測(cè)一般用must, will, should, may(might)或could，語(yǔ)氣依次遞減。
例17：Helen _____go on the trip with us but she isn’t quite sure yet. (2005安徽)
A. shall B. must C. may D. can
例18：-I’ve taken someone else’s green sweater by mistake.
-It ___ Harry’s. He always wears green. (2005廣東)
A. has to be B. will be C. mustn’t be D. could be
例19：That, I think, ____ be all that I want to say.
A. can B. could C. will D. ought to
分析： must的語(yǔ)氣最強(qiáng)，譯為“肯定”、“準(zhǔn)是”、“想必是”；should的語(yǔ)氣次之，譯為“很可能”、“應(yīng)該”，指按常理推測(cè)；may(might)譯為“也許、大概”，表示把握不大的推斷，后面常跟but。could的語(yǔ)氣最弱，譯為“也許”、“可能”。
對(duì)現(xiàn)在或客觀事實(shí)的否定推測(cè)，常用cannot譯為“根本不可能”, 表示推測(cè)的語(yǔ)氣非常肯定, may not, might not或could not譯為“可能不”、“也許不”，表示推測(cè)的語(yǔ)氣不很肯定。
例20：A left-luggage office is a place where bags ____ be left for a short time, especially at a railway station.
A. should B. can C. must D. will (2003全國(guó)卷)
例21：The World Wide Web is sometimes jokingly called the World Wide Wait because it ___be very slow.
A. should B. must C. will D. can (2005浙江)
分析： can 表示推測(cè)時(shí)常用于疑問(wèn)和否定句中，用于肯定句中常常表示理論上的可能性，用來(lái)表達(dá)事件或情況可能發(fā)生(但并不牽涉到是否真的會(huì)發(fā)生)。
例22：You might just as well tell the manufacturer that male customers __not like the design of the furniture.
A. must B. shall C. may D. need (2004上海春)
例23：--Isn’t that Ann’s husband over there?
--No, it _______ be him --I’m sure he doesn’t wear glasses. (2004全國(guó)Ⅰ)
A. can’t B. must not C. won’t D. may not
分析：might just as well表示“最好……，還是……為好”，說(shuō)明喜歡的可能性不大；根據(jù)后面的I’m sure可以看出，推測(cè)的語(yǔ)氣較強(qiáng)，故用can’t譯為“根本不可能”、“想必不會(huì)”，表示驚異、懷疑的感情色彩，常用于否定語(yǔ)氣較強(qiáng)時(shí)。
例24：Mr. Bush is on time for everything. How ______ it be that he was late for the opening ceremony？
A. can B. should C. may D. must (2001上海春)
分析：對(duì)現(xiàn)在或客觀事實(shí)的疑問(wèn)推測(cè), 用can或could，表驚異、懷疑、困惑、失望等感情色彩。
2、對(duì)過(guò)去事實(shí)的推測(cè)
對(duì)過(guò)去已發(fā)生事情的肯定推測(cè)常用 “must/may/might +have + v-ed”，“must+ have + v-ed”意思為“想必、準(zhǔn)是、一定是”，語(yǔ)氣非�？隙ㄇ抑荒苡糜诳隙ň�，“may/might+ have + v-ed” 意思為“也許、或許”表示推測(cè)的把握不大，只能用于肯定或否定句，不用于疑問(wèn)句；對(duì)過(guò)去的否定推測(cè)常用 “can/could /may’might not + have + v-ed”，意思為“不可能/可能沒(méi)做過(guò)……”；對(duì)過(guò)去的疑問(wèn)推測(cè)只用“can/could + have + v-ed”，意思為“可能已經(jīng)……”。
例25：He _______ have completed his work; otherwise, he wouldn’t be enjoying himself by seaside.
A. should B. must C. wouldn’t D. can’t (2005北京)
分析：根據(jù)后一分句判斷，前一分句應(yīng)該表示肯定完成了工作，故用“must+ have + v-ed”意思為“想必、準(zhǔn)是、一定是”，語(yǔ)氣非常肯定且只能用于肯定句。
例26：My sister met him at the Grand Theatre yesterday afternoon, so he _____ your lecture.(2000上海)
A. couldn’t have attended B. needn’t have attended
C. mustn’t have attended D. shouldn’t have attended
分析：must表推測(cè)時(shí)，不用于否定，needn’t have +v-ed 表示“本來(lái)沒(méi)有必要”，shouldn’t have +v-ed表示“本來(lái)不應(yīng)該”，“can/could not + have + v-ed” 意思為“不可能做過(guò)……”。
例27：--Do you know where David is? I couldn’t find him anywhere.
-- Well. He ______ have gone far----his coat’s still here.(2005湖北)
A. shouldn’t B. mustn’t C. can’t D. wouldn’t
分析：can’t have gone far 在此表示現(xiàn)在對(duì)過(guò)去所發(fā)生事情的否定推測(cè)，“現(xiàn)在不可能走遠(yuǎn)了”
3、對(duì)將來(lái)事實(shí)的推測(cè)
例28 -Are you coming to Jeff’s party﹖
-I’m not sure． I ________ go to the concert instead． (NMET2000)
A． must B．would C． should D． might
分析：由題意和下句中的 “I’m not sure” 可知這段對(duì)話中存在一種可能性推測(cè)，might可以用來(lái)表示一種比較委婉的可能性判斷
三、考查情態(tài)動(dòng)詞的虛擬用法
例29 ---I’ll tell Mary about her new job tomorrow.
---You________ her last week. (2004福建)
A. ought to tell B. would have told C. must tell D. should have told
分析：對(duì)過(guò)去發(fā)生事情的責(zé)備或遺憾應(yīng)用“情態(tài)動(dòng)詞+have + v-ed”，據(jù)此可排除答案A、C，而would +have +v-ed常用于過(guò)去的虛擬語(yǔ)氣中，should(ought to)+ have + v-ed”表示本應(yīng)該做某事而實(shí)際上沒(méi)有做，含有責(zé)備的含義。其否定式表示某種行為不該發(fā)生但卻發(fā)生了。故答案為D。
例30：He paid for a seat, when he ______ have entered free. (2005山東)
A. could B. would C. must D. need
分析：“could+ have + v-ed” 用于肯定句中，表示本來(lái)能夠做成某事的但結(jié)果沒(méi)能做成，含有遺憾的意味，側(cè)重有能力而沒(méi)能做成。“他花錢(qián)買(mǎi)了座位，而他本來(lái)可以免費(fèi)進(jìn)去的”。
例31：You should not have swum in that river. You ____ have been eaten by fish.
A. must B. may C. will D. might
分析：前一分句的should not have swum表示責(zé)備，后一分句則表明有被魚(yú)吃掉的可能性�！癿ight+ have + v-ed” 用于肯定句中，表示本來(lái)有可能做成某事但結(jié)果沒(méi)能做成，含有遺憾的意味，側(cè)重有某種可能性但沒(méi)能做成。
例32：-Catherine, I have cleaned the room for you.
-Thanks. You ______ it. I could manage it myself. (2005福建)
A. needn’t do B. needn’t have done C. mustn’t do D. shouldn’t have done
分析：“needn’t+ have + v-ed” 表示本來(lái)不必做某事而實(shí)際上做了某事，無(wú)批評(píng)責(zé)備之意，只是惋惜而已。如You needn’t have watered the flowers, for it is going to rain.你本不需要澆花的，因?yàn)樘炀鸵掠炅恕?/p>