【单选题】

{{I}}Questions 5 to 7 are based on the following conversation.At the end of the conversation, you will be given 15 seconds to answer the questions. Now listen to the conversation.{{/I}} What do the speakers mainly discuss

A、
A、notice on the bulletin boarD、
B．
A、book for a class the man is taking.
C．
A、chemistry class that is being taught.
D．The library reserve desk.