爱华网1. 当从句中的谓语动词是持续性的动作时,我们可以用while,when或as。
While / When / As I was walking down the street,I noticed a police car in front of thebank.我顺着马路往前走时,发现银行门前停着一辆警车。
2. 当从句中的谓语动词表示瞬间动作时,不可用while。
He was on the point of leaving when someoneknocked at the door. 他正要走,这时有人敲门。
3. 如果谈论两个长动作,最常用的是while。
While John was sitting biting his nails, I wasworking out a plan to get us home. 约翰坐在那里咬指甲时,我想出了一个回家的办法。
不过, as是可以用来说明两种正在发展或变化的情况的,这时as引导一个持续性的动作,主句中的动作与之同时进行。
As we talked on, he got more and moreexcited. 我们继续往下谈的时候,他越来越兴奋。
4. 如果表示两个短动作或事件同时发生,最常用的是as或justas,也可用when。
Just as he caught the ball, there was a tearingsound. 当他抓住球的时候,有一种撕裂的声音。
I thought of it just when you opened yourmouth. 就在你要说话的时候,我也想到了。
