while, when, as

maizai

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。 : `' } n3 k6 b　　　 As the day went on, the weather got worse.　 % a6 E0 s& h/ T* p0 ^　　　日子一天天过去，天气越变越坏。