ket的語(yǔ)法：could you please open the door

1. 過(guò)去進(jìn)行時(shí)

用來(lái)談?wù)撨^(guò)去某一時(shí)間正在發(fā)生的事情。

I was playing football at 3:30 yesterday.

用來(lái)討論過(guò)去某一時(shí)間同時(shí)發(fā)生的兩件事

He was doing homework while his sister was watching TV.

過(guò)去的情況和過(guò)去的情況發(fā)生在同一句話中：

Iwas doing homework when mysister cameto talk to me.

Someone knocked at the doorwhilemy mother was cooking.

否定句，疑問(wèn)句的表達(dá)方式：

He was not/wasn't working.

They were not/weren't speaking to each other.

Was he working?Yes, he was/No, he wasn't.

Were they speaking to each other? Yes, they were/No, they weren't.

2. can/can't/could/couldn't

有時(shí)，could可以作為can過(guò)去式使用

can/can't表現(xiàn)能力，用于當(dāng)今時(shí)代。

I canhelp you.(我可以幫助你)

could/couldn't在過(guò)去的時(shí)候，表達(dá)能力。

can/can't表示概率，用于當(dāng)今時(shí)代。

This can't be true.(這個(gè)不可能是真的)

could表示概率，用于過(guò)去，或者用于現(xiàn)在，但是語(yǔ)氣沒(méi)有can強(qiáng)烈

He couldn't go therewithout me.(他不可能不帶我一起去)

can/could也可用于今天的請(qǐng)求，不同之處在于，could比can語(yǔ)調(diào)更加委婉客氣

Can you help me please?

Could you please open the door?