区别状语从句中的when.doc

区别状语从句中的when, while和as的用法 一．when，while，as在时间状语从句中的区别：　　①三者均可表示“当……的时候”，如果主句表示的是短暂的动作，而从句表示的是一段时间，三者可通用。如：I met Kang Li as／when／while I was walking along the street．当我沿街散步时碰见了康丽。　　②when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： It was snowing when we got to the airport．当我们到达机场时，天正下着雪。（不能用while） 　　③as强调主句与从句表示的动作同时发生，as常表示“随着……”；“一边……，一边……；while强调主句表示的动作持续于while所指的整个时间内；when可指主、从句所述动作同时或先后发生。如： As the time went on，the weather got worse．（as表示“随着……”之意） He sang as he went along．他边走边唱。Please write while I read．我读的时候，请写下来。When he reached home，he had a little rest．回到家后，他休息了一会儿。 ④when用于表示“一……就……”的句型中（指过去的事情）。 somebody had hardly（＝scarcely） done …when．．．＝Hardly ／ Scarcely had somebody done …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。 二.when, while和as都可引导让步状语从句： ①．when引导让步状语从句，意为“尽管，虽然”相当于though或although: They stopped trying when they might have succeeded next time. ②while引导让步状语从句，相当于although ，是较为正式的书面语: While I am willing to go, I would like it better that you went. ③as引导让步状语从句必须倒装，从句中的表语，状语或动词原形置于句首，若表语为名词，前置时省略冠词。 Child as he is, he knows a lot. Much as I like it, I will not buy it, for it’s too expensive. Try as he might, he couldn’t find a job. 三.when和while可用作并列连词: ①when作并列连词，意为“突然，正在那个时候”常运用于以下句型中： Somebody be about to do…when… Somebody be on the point of doing…when… Somebody be doing… when… Somebody had done…when… We were having a meeting when someone broke in. We were about to set off on our way, when it suddenly began to rain. ②作并列连词，意为“而，却”，表示对比。 He likes pop music, while I am fond of music. 四.when和as用于原因状语从句中: ①when=since, now that… “既然” Why do you want a new job when you’ve got such a good one already? ②意为“因为”，指说话双方都知道的原因。 As he was not ready in time, we went without him. 组题练习： 1. Success came ______ she began to play leading parts in radio plays. A. While B. as C. when D. if 2. The atmosphere gets thinner and thinner ____