和谐英语

英语语法指导:比较while,when,as

2007-11-04来源:
  1)as, when 引导短暂性动作的动词。
  Just as / Just when / When I stopped my car, a man came up to me.
  2)当从句的动作发生于主句动作之前,只能用when 引导这个从句,不可用as 或 while。
  When you have finished your work, you may have a rest.
  3)从句表示"随时间推移"连词能用as,不用when 或while。
  As the day went on, the weather got worse. 
  日子一天天过去,天气越变越坏。