could：是 can的过去时，（询问是否可做某事）能，可以。用于疑问句中并不表示过去时，而是表示现在时。

would：是will的过去式，用于转述。将，将会，带出想象的结果。可用作情态动词will的过去式，用于陈述语气时可表示过去的意志、决心、习惯或反复性的动作。

相关介绍

I could do it now, if you like.

如果你愿意的话，我现在就可以做这事。

The operation could prolong his life by two or three years.

这次手术可使他多活两三年。

He said he would be here at eight o'clock.

他说他将在八点钟到达这里。

I would very much like to see you again.

我很想再见到你。