题型：填空题 题类：常考题 难易度：容易
广东中考人教新目标（Go for it）八年级上学期Units 4－6教材梳理
表示"当……时候"，既指时间点，又指一段时间，when 引导的时间状语从句中的动词可以是终止性的也可以是延续性的。
When the teacher came in, the students were talking.
When she arrives, I'll call you.
表示"当……时候"，仅指一段时间，从句中的动作必须是延续性的，一般强调主从句的动作同时发生， while还可以作并列连词，意为"而、却"，表示对比关系。
Lisa was singing while her mother was playing the piano.
Tom is strong while his younger brother is week.
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