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【归纳拓展】 as作连词的用法： (1)作“当……的时候”，引导时间状语从句。注意与when, while的用法区别。 ① when作“当……的时候”解，可以指较短的(一点)时间，也可指一段时间，即非延续性动词。 When he was at college，he could speak several foreign languages. When the clock struck twelve，all the lights in the street went out. ② while常表示一段较长的时间或一个过程，即延续性动词。强调主句谓语动词与从句谓语动词同时发生。 Work while you work.Play while you play. ③但属下列情形时，只用as，而不用when或while。 a．用于表示同一个人的两个动作交替进行，指“一边……，一边……”。 The girl dances as she sings on the stage. He looked behind from time to time as he went forward. b．表示两个同步发展的动作或行为，译为“随着……”。 As time went on/by，she became more and more worried. As children get older，they become more and more interested in the things around them. c．后接名词表示某一年龄段时，用as。 As a young man，he was active in sports. (2)as＝since，作“既然”“由于”解，引导原因状语从句，常用来表示已为人们所知或显而易见的原因或理由。 As/Since you’re not feeling well，you may stay at home. As he wasn’t ready in time，we went without him. (3)as＝in the way that，作“像”“按照……的方式”解，引导方式状语从句。 He speaks English as Americans do. Remember，you must do everything as I do. (4)用于as...as...或not so/ as...as...中，前一个as是副词，后一个as是连词，引导比较状语从句。 They helped the old man as often as possible. I don’t speak English so/ as well as he does. (5)作“虽然”“尽管”解，引导让步状语从句。常用倒装语序，即adj./adv./n.＋as ＋主语＋谓语＋主句。 Tired as they were，they walked on.Child as he is，he knows a lot.(child前不用冠词) as作关系代词 (1)引导非限制性定语从句，作“正如”“这一点”解。 He is very careful，as his work shows. As is wellknown，Taiwan belongs to China. as的这种用法，请看下面的高考题： ________ is known to everybody，the moon travels round the earth once every month. A．It | 
