ket的語法：could you please open the door

1. 過去進行時

用來談論過去某一時間正在發(fā)生的事情。

I was playing football at 3:30 yesterday.

用來討論過去某一時間同時發(fā)生的兩件事

He was doing homework while his sister was watching TV.

過去的情況和過去的情況發(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，疑問句的表達方式：

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，could可以作為can過去式使用

can/can't表現(xiàn)能力，用于當今時代。

I canhelp you.(我可以幫助你)

could/couldn't在過去的時候，表達能力。

can/can't表示概率，用于當今時代。

This can't be true.(這個不可能是真的)

could表示概率，用于過去，或者用于現(xiàn)在，但是語氣沒有can強烈

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

can/could也可用于今天的請求，不同之處在于，could比can語調(diào)更加委婉客氣

Can you help me please?

Could you please open the door?