Read and choose. (根据上下文，找出适当的句子，将其标号填在横线上)

A. Hold on,  please.           

B. I'm doing my homework, now.

C. Who's that?                

D. What is he doing?          

E. It's Mary here.

Mary: Hello.

Helen: Hi.  This is Helen speaking.

Mary: 1. ________________ Can I speak to your brother, Peter? 2. ________________

Helen: He is reading a book. 3. ________________ Peter, it's for you.

Peter: OK. I'm coming. Thank you. It's Peter here. 4. ________________

Mary: This is Mary. 5. ________________I have a question.