1 Is this museum _THE ONE (THAT / WHICH )_you visited the other day ?
THAT / WHICH 是visited的宾语。the one是this museum的表语
2 This is the museum__WHERE _we saw an exhibition the other day.
WHERE== in which == in the museum,是 saw an exhibition 的地点状语。
第一个句子是填where
下一个必须选that 因为后面的定语从句缺一个名词性的东西,只有that可以充当名词