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      19.8 比較while, when, as
      ?
      1)as, when 引導(dǎo)短暫性動作的動詞。
          Just as / Just when / When I stopped my car, a man came up to me.
      2)當(dāng)從句的動作發(fā)生于主句動作之前,只能用when 引導(dǎo)這個從句,不可用as 或 while。
          When you have finished your work, you may have a rest.
      3)從句表示"隨時間推移"連詞能用as,不用when 或while。
          As the day went on, the weather got worse. 
          日子一天天過去,天氣越變越壞。















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