选择合适的句子补全对话。                                 

A. Yes, he is. B. Do you know Mr Brown? C. He's our music teacher. D. No, he isn't.

Sarah: 

Linlin: No, I don't. Who's he?

Sarah: 

Linlin: Is he old?

Sarah: He's young.

Linlin: Is he friendly?

Sarah: 

Linlin: Great! I like friendly teachers.