a.What were you doing when it rained.b.What were you doing while it was raining.

问题描述:

a.What were you doing when it rained.b.What were you doing while it was raining.

两个句子都对.第一句用 when it rained 只是表示“当下雨的时候”,第二句用 while it was raining 强调在下雨进行的时候.