( )是指调查者通过到现场观察被调查者的言语和行为，从而采集相关信息的方法。

A．当面调查询问法

B．电话调查法

C．会议调查询问法

D．观察法

Speaker A: Hello! Professor Freeman’s secretary. Can I help you
Speaker B: ().

A. Hello! Can you find Professor Freeman for me

B. Yes. I hope you can help me. My name is John Smith.

C. Good afternoon I’d like to make an appointment to see the professor on Thursday, please.

D. Thank you. Professor Freeman knows me well.