as从句前后的时态有进行时和一般时
As作连词引导时间状语从句时,着重强调主句和从句中的动作同时发生,并且从句通常放在主句之前。归纳起来有下列两种情况:
1)状语从句的谓语动词是持续性动词,从句时态常用进行时态。如:
①As he Was waiting, he suddenly heard a voice from above
②As Bethune and the other doctors were climbing the hills, they could see the enemy entering the village in the valley below.
2)状语从句的谓语动词是终止性动词,从句时态常用一般时态。如:
①As she stood there, she heard the firstbell.
②As they looked up, they saw another cloud coming towards them.
③As they watched. it came nearer and nearer.
基本上要保持一致，比如as后面是过去时，前面也是过去时。
