选择下列问句的正确答语，将序号填入括号里。
1. What's he doing?[ ]
A. He is at home.
B. He eats dinner.
C. He is picking up leaves.
2. Is she collecting leaves?[ ]
A. Yes, he is.
B. No, she isn't.
C. No, she doesn't.
3. Is she writing a report?[ ]
A. No, she isn't. She's writing a letter.
B. Yes, I am.
C. No, he isn't.
