2018中考英语：英语语法状语从句专项练习及答案

when可以和延续性动词连用，也可以和短暂性动词连用;而while和as只能和延续性动词连用。如：

When he came in, his mother was cooking.

When (While) we were at school, we went to the library every day.

when从句的谓语动词可以在主句谓语动作之前、之后或同时发生;while和as从句的谓语动作必须是和主句谓语动作同时发生。

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 don t 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。

在将来时从句中，常用when，且从句须用一般时代替将来时。

①You shall borrow the book when I have finished reading it.在我读完这本书后，你可以借阅。

②When the manager comes here for a visit next week，Ill talk with him about this.下周，经理来这参观时，我会和他谈谈此事。

when用于表示 一 就 的句型中(指过去的事情)。

sb.had hardly(=scarcely) done sth.when...=Hardly / Scarcely had sb.done sth.when...

①I had hardly /scarcely closed my eyes when someone knocked at the door.=Hardly / Scarcely had I closed my eyes when someone knocked at the door.我刚一闭上眼，就有人在敲门了。

②I had hardly /scarcely entered my room when the telephone rang.=Hardly /Scarcely had I entered my room when the telephone rang.我刚一走进房门，电话就响了