we used to study in the old building which was broken down .为什么which不能用where

题目

we used to study in the old building which was broken down .为什么which不能用where

答案

这个句子的后半句 本来应该是 the old building was broken down .
the old building 作主语 只能用which或that来 替换.
而where是作地点状语 这个句子缺主语 所以用 which