The reason behind the confusion should be thatA．th

单项选择题

Questions 4 to 6 are based on the following conversation. At the end of the conversation, you will be given 15 seconds to answer the questions.

The reason behind the confusion should be that

A．the man mixed up the two classes.
B．the man didn’t switch class in time.
C．there had been a mistake during the add/drop process.
D．the man didn’t fill the add/drop form.