情態(tài)助動詞用法簡述

dare, need

① dare作情態(tài)動詞用時, 常用于疑問句、否定句和條件從句中, 過去式形式為dared。

eg. How dare you say such horrible words to me?

② need 作情態(tài)動詞用時, 常用于疑問句、否定句，相當(dāng)于肯定句中一般用must, have to, ought to, should。

eg. Need I finish the work today?

Yes, you must. / No, you needn't.

③ dare和 need作實義動詞用時， 有人稱、時態(tài)和數(shù)的變化，在肯定句中，dare后面常接帶to的不定式，在疑問句和否定句中，dare后面可接帶to或不帶to的不定式，而need后面只能接帶to的不定式。

eg. She doesn't dare (to)answer.

She needs to cook dinner for her sisters.

五. shall, should

① shall 用于第一人稱，征求對方的意見。

eg. What shall I do ?

② shall 用于第二、三人稱，表示說話人給對方的命令、警告、允諾或威脅。

eg. You shall be punished,you bad boy!

六. will, would

① 表示請求、建議等，使用would使語氣更加緩和。

eg. Would you give me a cup of coffee, please?

② 表示意志、愿望和決心。

eg. I will never do that again.

③ would表示過去反復(fù)發(fā)生的動作或某種傾向。

eg. During that summer, he would visit me every other day.

④ 表示估計和猜想。

eg. It would be about may when she come back to China.

七. should, ought to

① should表示“應(yīng)該”，ought to表示義務(wù)或責(zé)任，語氣更嚴(yán)重。

eg. I should help her because she is in trouble.

You ought to take care of her because she is your daughter.

② 表示勸告、建議和命令，should, ought to可通用，但在疑問句中常用should。

eg.Should I open the window?

③ 表示推測， should , ought to (客觀推測), must(主觀推測)。

eg. She must pass the exam. (斷定)

She ought to/should pass the exam.(不太肯定)