--I visited the Purple Mountain Observatory last Sunday.Why didn’t you tell me earlier

问题补充：

--I visited the Purple Mountain Observatory last Sunday.

--- Why didn’t you tell me earlier?

A. Have a good time.

B. I hope so.

C. You did?

D. It’s kind of you.

答案：

A. Have a good time.

B. I hope so.

(答案→)C. You did?

D. It’s kind of you.

解析：句意：我上周日参观了紫金山天文台。真的？你为什么不早点告诉我？A玩得开心，B我希望如此，D你太友好了。根据题意选C。