Question

如何区分when.while.as.before after.as soon as until时间状语从句的主句和从句

Answer 1

1、while, when和as
①as, when 引导短暂性动作的动词。Just as / Just when / When I stopped my car, a man came up to me.
②当从句的动作发生于主句动作之前，只能用when 引导这个从句，不可用as 或 while。When you have finished your work, you may have a rest.
③从句表示"随时间推移"连词能用as，不用when 或while。As the day went on, the weather got worse.
日子一天天过去，天气越变越坏。
2、until和till
①肯定形式表示的意思是“做某事直至某时”，动词必须是延续性的。
I slept until midnight. 我一直睡到半夜时醒了。 Wait till I call you. 等着我叫你。
在肯定句中可用before代替。
Let's get in the wheat before the sun sets.
②否定形式表达的意思是“直至某时才做某事”。动词为延续性或非延续性都可以
She didn't arrive until 6 o'clock. 她直到6点才到。 Don't get off the bus until it has stopped. 公共汽车停稳后再下车。 I didn't manage to do it until you had explained how.直到你教我后，我才会做。
③ Until可用于句首，而till通常不用于句首。
3、表示“一…就…”的 结构
hardly/scarcely…when/before, no sooner…than和as soon as 都可以表示“一…就…”的意思，例如：As soon as I got home, it began to rain.
我一回到家天就开始下起雨来了。