when引导的从句的谓语动词可以是延续性的动词,又可以是瞬时动词.并且when有时表示“就在那时”.
例如:
When she came in,I stopped eating.她进来时,我在吃饭.(瞬时动词)
When I lived in the countryside,I used to carry some water for him.当的住在农村时,我常常为他担水.(延续性的动词)
We were about to leave when he came in.我们就要离开,就在那时他进来了.
While引导的从句的谓语动作必须是延续性的,并强调主句和从句的动作同时发生(或者相对应).并且while有时还可以表示对比.例如:
While my wife was reading the newspaper,I was watching TV.(was reading是延续性的动词,was reading和was watching同时发生)
I like playing football while you like playing basketball.我喜欢踢足球,而你喜欢打篮球.(对比)
as soon as
as soon as 意义为“一…就” ,引导时间状语从句,可置于句首或句末,最常见的用法是在将来时态的情境中,遵守“主将从现”,的原则,i.e.
I'll write you as soon as I get there.
我一到那儿,就给你写信.
They will post the tickets to me as soon as they receive my cheque.
他们收到我的支票后就立刻把票寄给我.
Let us start as soon as he comes.
等他一来我们就动身.