文档介绍：情态动词
The usages of modal verbs(Fill in the chart after reading the materials.)
model verbs
Basic Chinese meaning
usages
Examples
1.
Can
could
(5种用法)
“能”,“会”
1)表能力 
Both of them can swim.
注 1 can 和be able to 同义,但can只用于现在式和过去式(could)。be able to可以用于各种时态。
They will be able to tell you the news soon. 他很快就能告诉你消息了。
注2:was(were) able + 不定式不仅表示过去能做某事,而且一般都是成功行为(表成功地做了某事),这时不能用could 替换,不过在否定句中二者可以互换。
1 . He didn’t agree with me at first but I was able to persuade 。
2. He was able to flee Europe before the war broke out. = He managed to flee Europe before the war broke out.
3 . He wasn’t able to (or couldn’t) see me before I 。
2)提出委婉的请求= may,此时could和can
--- Could/Can I have the television on?
--- Yes, you can. / No, you can't.
没有时间上的差别,could 更委婉。(但是在回答中不可用could)
3)can和could在否定句或疑问句中表示推测或怀疑。can较could更加表示说话人肯定的语气。
注 can不能用在肯定句中表示推测,它在肯定句中只表示能力。 
例如,只能说“He may be at home(他可能在
家)”,不能说“He can be at home”。
(1)can/could+do (对现在情况的推测)
He can’t be at work. 他不可能在上班。
Can what he said be true? 他说的话靠得住吗?
(2)can/could+be doing
表示对目前正在进行行为的猜测。
例 1 They cannot be cleaning the room at the moment. 他们现在不可能在打扫房间。
例 2 What could they be doing yesterday afternoon? 昨天下午他们可能在做什么呢?
(3) can/could + have done,都可表示对过去某事物的猜测,can 只能用于疑问句和否定句中,而could既可以用于肯定句,也可用于否定句和疑问句中,could + 完成时动词还可表示事实上没有实现的行为,带有责备的含义。
例 1 You couldn’t have seen him yesterday because he was out of the town.
你不可能在昨天见到他,因为他出城了。
例 2 Can he have done the experiment? 他会做完实验了吗?
例 3 John can’t have forgotten my name. 约翰不可能忘了我的名字。
例 4 He could e 。
4)could 用在wish后的宾语从句或虚拟条件句中
I wish I could sleep all day. 我希望能睡一整天。
If my family were rich,I could have bought the car. 如果以前我家富有,我已买车了。
5)cannot (或 couldn’t )和too…连用表示“…也不过分…”意
We can not mend this book too strongly. 这本书我们无论怎样推荐都不过分。
I cannot see you too often. 我和你见面次数越多越好。
2.
maymight
(四种用法)
可以
1) 表示允许或请求= can/could
May I use your pen ?
(Yes, you may.
No, you mustn’t.)
2)表示没有把握的推测(用于肯定句或