在横线上填写适当的句子，补全对话。

A: Hi, Bob!

B: Hi, Mary!

A:

B: It's a pencil.

A:

B: P-E-N-C-I-I.

A:

B: It's yellow.

A: Is this yours?

B: It's hers. Mine is in my pencil box.

A: Where is your pencil box?

B: I don't know.

A: Is it in your schoolbag?

B: Oh, yes, it is.

A: You're welcome.