I asked him what had happened 为什么要用had happened 而不直接用happened

问题描述:

I asked him what had happened 为什么要用had happened 而不直接用happened

主句时态是过去式,从句中要用过去完成时,是指在“问”这个动作进行之前发生的事,“问”的动作已经过去了,事情是过去的过去发生的,即用had happened.