题目内容：
13.Professor: First of all, allow me to introduce Professor John Brown from Cambridge.Student: _____
(3分)
A. Hello, Mr. John Brown. What brings you here?
B. Morning, Prof. Brown. May I have a question?
C. Hi, Prof. John Brown. Can I ask what your specialty is?
D. Hello, Mr. Brown. Are you a doctor?
参考答案：