选择合适的选项补全对话。(每个选项只能选一次)

A. It's on the second floor.

B. Yes, it is.

C. No, it's the first floor

John: Excuse me．Is it the second floor?

Tom:

John: Is that the teachers'  office?

Tom:

John: Where is the library?                       

Tom:                                 

John: OK．Thanks．