状语从句练习易混引导词while, when, as的区别：1.when既可以指时间点,与瞬间动词连用，也可以指时间段，与延续性动词连用（=while）。如：When he came in, his mother was cooking.When (While) we were at school, we went to the library every day.While表示时间段,因此，while 从句的谓语动词要用延续性动词。如：Please dont talk so loud while others are working.As与when用法相似，但着重强调主句动作与从句动作同时发生，有随着或一边一边之意。如：As you get older, you get more knowledge.随着年龄的增长，你获得的知识就越多。2Because,as,since 的区别：Because用于表示直接原因,回答why提出的问题，语气最强；As用于说明原因, 着重点在主句，常
