He had finished his homework before he watched TV

问题描述:

He had finished his homework before he watched TV
对划线部分提问 划线部分为before he watched TV
____ ____ ____ ____ his homework?
四个空格
可以用when吗
我记得现在完成时是用how soon提问的...

When did he finish
用how soon 提问的是将来的一段时间
这里问的是时间的点