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常见的时间状语从句
由when, while, as引导的时间状语从句
When you think you know nothing, then you begin to know something.
当你以为自己一无所知的时候，你就是在开始知道一些事物了。
Strike while the iron is hot.　趁热打铁。
Will you watch my clothes while I have a swim？
我游泳的时候，请你照看一下我的衣服。
You can feel the air moving as your hand pushes through it.　
当你的手在空气中挥动的时候，你就能感觉到空气在流动。
Our headmaster laughed as she spoke.
我们的校长边谈边笑。
注意：1。when, while和as的区别：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”。
   When she came in, I stopped eating.她进来时，我在吃饭。
   When I lived in the countryside, I used to carry some water for him.
住在农村时，我常常为他担水。
We were about to leave when he came in.
我们就要离开，就在那时他进来了。
2。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。
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。
3。As表示“一边……一边”，as引导的动作是延续性的动作，一般用于主句和从句动作同时发生；as也可以强调“一先一后。
   We always sing as we walk.
我们总是边走边唱。
   As we was going out, it began to snow.
当我们出门时，开始下雪了。
（as强调句中两个动作紧接着先后发生，而不强调开始下雪的特定时间）