英语语法之情态动词
情态动词
1. may/might表示允许和可能:
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a) 允许: 询问或说明一件事可不可以做.
May I trouble you with a question?
You may take this seat if you like.
He asked if he might glance through myalbum.
You might as well speak your mind. (比may…显得婉转一些)
b) 可能: 表示一件事或许发生(或是某种情况可能会存在).
You may walk ten miles without seeing ahouse.
She was afraid they might not like theidea.
A bad thing might be turned to goodaccount.
c) might 表示请求:
Might I ask for a photograph of your baby?(比May I …更客气一些)
2. can’t, couldn’t表示否定的推测:
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She can’t be serious.
A more suitable book can’t be found. (It isnot possible to find a more suitable book.)
He couldn’t (can’t) be over fifty.
3. should, ought to: 表示应该做的事, ought to比should口气稍重一些.
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You should (ought to) do as he says.
You shouldn’t (oughtn’t to) talk like that.
但这两者间也有一些差别, 在表示责任, 义务等该做的事情时, 常用ought to, 在表示某件事宜于做时, 多用should, 在下面的句子中这两个词就不宜换用:
You are his father. You ought to take careof him.
We should not use too many big words in oureveryday speech.
4. will, would
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5. shall, should表示意愿
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6. 情态动词后接进行式, 完成式和完成进行式:
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a) 情态动词可以和动词的进行式构成谓语, 表示”应该正在…”, “想必正在…”这类意思:
Why should we be sitting here doingnothing?
This isn’t what I ought to be doing.
She might still be thinking about thequestion you raised.
They must (may) be waiting for us, let’shurry up.
They can’t be using the room now.
b) 情态动词有时和动词的完成形式构成谓语, 表示”应当已经…”, “想必已经…”这类意思:
I should have thought of that.
They shouldn’t have left so soon.
She must have arrived by now.
You needn’t have told them that.
Where can (could) he have gone?
He can’t have finished the work so soon.
He may not have achieved all his aims. Buthis effort is praise-
worthy.
We ought to have give you more help.
c) 情态动词间或也可以和一个动词的完成进行式构成谓语,表示”应当一直在…”, “想必一直在…”这类意思:
They are sweating all over. They must havebeen working in the fields.
They may have been discussing the problemthis morning.
You should have been waiting for us. Whyhaven’t you?
She couldn’t have been swimming allday.
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常考知识点:
1 can 的理解和翻译
You cannot be careful when you drive a car.
A. very B. too C. so D. enough
你开车时越小心越好。（97.6-32,B对）
can有很多含义，它可以用来表示可能性（possibility）。该句相当于It's impossible that you are too careful when you drive a car. 即：“你开车时太小心这种情况是不可能的”。句型“cannot/never/hardly...too＋...”表达强烈的肯定，常常译成“越...越好”，“再...也不过分”。例如：
We can not stress the importance of thetheory too much.
这一理论的重要性，怎样强调都不过分。
The important role people played in historycan never berated too much.
人民在历史上所起的作用，无论怎样评价都不会过高。
A book can hardly last too long.
好书定能永远流传下去。
The effect of science and technology onsocial progress can never be estimated enough.
科学技术对社会进步所产生的影响，无论怎样评价都不过分。
2 “情态动词＋完成式”的用法
You ______ her in her office last Friday;she's been out often for two weeks.
A）needn't have seen B）must have seen
C）might have seen D）can't have seen
你不可能在上星期五看见她在办公室，她离开镇子已经两星期了。(96.1-23,D对)
The room is in a terrible mess; it ______cleaned.
A）can't have been B）shouldn't have been
C）mustn't have been D）wouldn't have been
房间乱极了，不可能有人打扫过。(96.6-31,A对）
It was very kind of you to do thewashing-up, but you ______ it.
A）mustn't have done B）wouldn't have done
C）mightn't have done D）didn't have to do
谢谢你把东西洗了，但是你本来没有必要洗的。(98.6-44,D对。...but you didn't have to do it 相当于but you needn't have done it )
Research findings show we spend about twohours dreaming every night , no matter what we ______ during the day.
A）should have done B）would have done
C）may have done D）must have done
研究结果表明：不管我们白天做了什么，我们每晚大约有两个小时在做梦。(99.1-54,C对）
3 may / might as well 表示“因为没有更好、更有趣或更有用的事可做，就做某事”
If you don't like to swim, you ____ stay athome.
A) should as well B) may as well
C) as well D) would as well
如果你不喜欢游泳，也可以留在家嘛。(95.1-60, B对。)
