根据对话内容，在每个空白处填入一个适当的句子，使对话完整、合乎情境。

A: Hi, Martin.

B: Hello, Jim.

A: ?

B: I'm in a shop

A: ?

B: I'm buying a present.

A: ?

B: It's a pen

A: ?

B: No, it's not for my sister. It's for Tom.

A: ?

B: He's my cousin. It's for his birthday.