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.
