1. (2019七上·元宝期中) 根据对话情境，用适当的句子补全对话

A: Excuse me, Nancy. A baseball is under the desk. ?

B: A baseball? ?

A: It's white.

B: No, it's not mine. I think it's Alan's.

A: Alan??

B: He is my friend. And he is a student in Class Three.

A: Is he in his classroom now?

B: Sorry, I don't know.

A: ?

B: His phone number is 13897873125.

A: Thank you.

B: .