(1)as 是连词,意思是"当……的时候,一面……一面",(强调同时,一般连续时间不长),如:
As we were talking about Titanic, our teacher came in. 正当我们谈论"泰坦尼克号"这部电影时,教师进来了。
The students sing as they go along. 学生们边走边唱。
(2)When和as一样都是连词,注意它们的不同。如when"当……的时候"(一般表示动作紧接着发生);
"那时"(等立连词,前有逗号分开)I stayed till sunset, when it began to rain. 我一直呆到太阳下山,那时天开始下雨了。
(3)while是"当……时候;和……同时"(强调同时发生,一般连续时间较长)例如:While I was watching TV, he was reading. 当我在看电视的时候,他正在看书。While there is life, there is hope. 有生命就有希望。
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