选择恰当的句子补全对话。

Ms Smart: Good afternoon, Lingling.

Lingling: , Ms Smart.

Ms Smart: ?

Lingling: I'm fine, thank you.

Ms Smart: ?

Lingling: It's a ball.

Ms Smart: What's that?

Lingling: .

Ms Smart: Sit down, please, Lingling.

Lingling: .

A. It's a schoolbag B. Thank you C. Good afternoon D. How are you E. What's this