by the time l reached home my brother --- to work

问题描述:

by the time l reached home my brother --- to work
a\ went
b\ has gone
c\ had gone
d was gone
为什么答案是c
理由越详细越好,好的有赏

by the time表示时间点,时间点是I reached home,表示是过去的时间点.所以要用过去,排除b,因为by表示截止到时间点,用完成时,排除ad,选C