根据对话内容，完成下列各题，将正确答案的序号写在题前括号里。
A: Look at the baby kangaroo. It's sleeping.
B: What about the mother kangaroo? What's she doing?
A: She's jumping.
B: Do you see any elephants?
A: Yes. An elephant is drinking water with its trunk.
1. What is the baby kangaroo doing？[ ]
A. It's jumping.
B. It's sleeping.
2. — ？ —She's jumping.[ ]
A. What is the mother kangaroo doing?
B. What is the monkey doing?
3. — ？ —It's drinking water.[ ]
A. What is the elephant doing?
B. What are they doing?
确定的隐函数，则