这里有一道定语从句的,

Is this the museum ____ we visited three years ago?初学定语从句者改成陈述句比较容易看出句子结构,This is the museum ____ we visited three years ago.因为visit缺少宾语,填写which/that,可以省略,答案选D
如果选A,应该是Is this museum ____ we visited three years ago?
where和in which在下面这种情况时不能替换 Put the book where it was.（这是一个地点状语从句,where=in the place where=in the place in which）,其他时候基本可以替换.