一、考点聚焦%
1、时间状语从句
（1）as、when、while用法。
as表示“当…的时候”, 往往和when/ while通用, 但它着重强调主句与从句的动作或事情同时或几乎同时发生。 She came up as I was cooking.（同时）
The runners started as the gun went off.（几乎同时）
when （at or during the time that ）既可以表示在某一点的时候, 又可表示在某一段时间内, 主 句与从句的动作或事情可以同时发生也可以先后发生。 It was raining when we arrived.（指时间点）When we were at school, we went to the library every day.（在一段时间内）
