根据情景选择相应的句子。
1. 当你和别人交谈，想询问对方的职业时，你应该说：（   ）
A. What do you do? B. What does she do?
C. What does he do?
2.当你告诉别人你是一名警察时，你应该说：（   ）
A. You are a policeman.   B. He is a policeman.
C. I am a policeman.
3.当你询问对方是否一名兽医时，你应该说：（   ）
A. Is she is a doctor? B. Is he is a doctor?
C. Are you a vet?
4. (接第3小题)对方作肯定回答时，他应该说：（   ）
A. Yes, he is. B. Yes, she is.
C. Yes, I am.