As is known to all,___ there is pollution ,there is harm.A.where B.that where

题目

As is known to all,___ there is pollution ,there is harm.A.where B.that where
B 为什么

答案

这一句话里面,As is known to all只是一个插入语,只看 ___ there is pollution ,there is harm.
所以缺个主语,只用where就够了