專升本英語(yǔ)語(yǔ)法基本知識(shí)（情態(tài)動(dòng)詞）

此前，為大家推送過專升本英語(yǔ)語(yǔ)法基本知識(shí)狀語(yǔ)從句的內(nèi)容，今天為大家?guī)?lái)了情態(tài)動(dòng)詞的部分，希望對(duì)大家有所幫助。

情態(tài)動(dòng)詞有can, could, may, might, must, should, ought to, need, dare, had better, would rather 等。情態(tài)動(dòng)詞相當(dāng)于助動(dòng)詞，不能單獨(dú)使用，必須再接動(dòng)詞原型。

1. can, could表示能力、允許、客觀可能性。

注意:表能力時(shí)could是can的過去式；表允許時(shí)could比can更委婉，表客觀可能性時(shí)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. 真金不怕火練

2. may, might表示允許、猜測(cè)。

[注意]表允許時(shí)might比may更委婉;表客觀可能性時(shí)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在外邊待的很晚)

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 “不許、不準(zhǔn)”)

3. must

1)表示可能性"肯定"、"準(zhǔn)是"，其否定形式是can't

2)表示"必須"。must只用在一般現(xiàn)在時(shí)和一般將來(lái)時(shí)，此時(shí)must= have/has to,而have to可以用在任何時(shí)態(tài)。其否定形式needn't

3)mustn't表示"千萬(wàn)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一般疑問句的否定用needn't來(lái)回答)

He has to/must tidy up the room everyday. (tidy up打掃干凈)

You mustn't talk like that to your parents.

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