A、  B、  C、  C(A)只是叙述了一般的事实，并没有回答提问。(B)利用了与画廊相关的artist，但是整体意思与提问无关。(C)“要参加的会议太多了”这句话间接地告诉了没能参观美术馆的原因，因此正确。

Whose car is that parked outside?
(A)The park is full of flowers.
(B)It’s been a long day.
(C)I think it’s my brother’s.

Did you visit the art gallery while you were there?
(A)Yes, it is closed on Mondays.
(B)Nobody has seen the artist yet.
(C)I had too many meetings to attend.