i heard him ()(sing)at that moment i heard he ()(sing)at that time第一个填sing 第二个填wassinging.麻烦大家帮我讲讲!

问题描述:

i heard him ()(sing)at that moment i heard he ()(sing)at that time第一个填sing 第二个填was
singing.麻烦大家帮我讲讲!

第一个 由于是 at the moment 就是此刻 所以应该用进行时态 hear sb doing sth.而第二个 at that moment that 指代那个时刻 所以是过去的时间正在唱歌 必须用过去进行时态 was doing