Read and write. （读下面的对话并把句子补充完整）

Jack: Hi.

Peter: Hello.  This is Peter speaking.  Is Jack here?

Jack: It's Jack here.

Peter: Jack, what are you doing?

Jack: I'm watching TV. How about you?

Peter: I'm doing my homework.  Can I speak to your sister, Mary?

          I have a question about the homework. What is she doing?

Jack: She is cleaning the room. Hold on, please.

Peter: OK. Thank you.

1.      Peter is                                   

2.     Jack is                                    

3.     Mary is                                   

第一类建筑物引下线间距为多少米才符合要求。