知识点讲解

专升本英语语法基本知识（情态动词）

发布时间：2020/04/03 14:06:29 阅读量：4130

此前，为大家推送过专升本英语语法基本知识状语从句的内容，今天为大家带来了情态动词的部分，希望对大家有所帮助。

情态动词有can, could, may, might, must, should, ought to, need, dare, had better, would rather 等。情态动词相当于助动词，不能单独使用，必须再接动词原型。

1. can, could表示能力、允许、客观可能性。

注意:表能力时could是can的过去式；表允许时could比can更委婉，表客观可能性时could 可能性比can 小。

eg:She is only four, but she can read.

This sort of thing can't go on.

I couldn't follow her speech.

Could you lend me your bike?

Fire can't destroy gold. 真金不怕火练

2. may, might表示允许、猜测。

[注意]表允许时might比may更委婉;表客观可能性时might可能性比may小。

eg:The dialect of one province may be quite different from that of the next one.

Students may not stay out after midnight without written permission. (stay out在外边待的很晚)

He asked his mother if he might go out to play.

"May I open the window?" "Yes, please./ Please don't./ No, you mustn't." (mustn't “不许、不准”)

3. must

1)表示可能性"肯定"、"准是"，其否定形式是can't

2)表示"必须"。must只用在一般现在时和一般将来时，此时must= have/has to,而have to可以用在任何时态。其否定形式needn't

3)mustn't表示"千万不要"、"一定不要"。

eg:He must be a student.

Teachers always tell us we must do everything step by step.

--Must I go tomorrow?

--No, you needn't.(Yes, I'm afraid so. must一般疑问句的否定用needn't来回答)

He has to/must tidy up the room everyday. (tidy up打扫干净)

You mustn't talk like that to your parents.