专升本英语语法-情态动词(一)
一、常见的情态动词有:
can 能;may 可以;will,would (表意愿);need 需要;dare 敢;must 必须;
have to 不得不 ;shall,should 应该(表义务);ought to 应该
二、can,could 的用法
-----No, I can't.
1. 表能力,有“能”、“会”、“能够”的意思
Can you drive a car?
-----Yes, I can.
2. 表允许,在口语中代替 may,有“可以”的意思
Can I use your bike?
3. 表示可能性,常用于否定句和疑问句
Can it be true?
Today is Sunday. He can't be at school.
4. 过去式 could 表示的语气更加委婉、客气
Could I come to see you tomorrow?
5. can 和 be able to 的比较
1)can 只有一般现在时和一般过去时两种时态(could),其他时态要用 be able to
的形式
I haven't been able to get in touch with her.
2)通常 can 和 be able to 可以互换
He will come if he can.
二、may,might 的用法
-----Yes, please.
1. 表示许可或征求对方的许可,有“可以”的意思。
You may go now.
May I use your computer?
2. 回答以 may 开头的疑问句有如下表达法:
May I smoke here?
--Yes, you may.
------No, you can't.
3. 表示猜测,通常只用于陈述句
You may be right. 你可能是对的。
4. 过去式 might 表示的语气更加委婉、客气
Might I use your pen for a while?
5. 在口语中 can 可以代替 may 表示许可,但 can 较随便,may 更正式
Can I use your bike, John?
May I have a look at your license please, sir?
------No, you mustn't. ------No, you'd better not.