【正确答案】 C

【答案解析】[听力原文]
   M: Good morning. Will you book a plane ticket to London for me?
   W: Yes, sir. What time would you like to leave?
   M: The 21st of December.
   W: There are several flights available.
   M: Morning flights will be perfect.
   W: Yes, sir. There is a flight available on that day, at 10:00 am.
   M: Fine. I'll take that flight, then.
   What does the conversation talk about?
[考点] 细节题
问题问的是对话讨论的主题是什么。根据男士所说Will you book a plane ticket to London for me?可知，男士准备订机票。故选C。