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. Now, listen to the conversation.
What does the professor imply

A.It is not acceptable to miss class time.
B.The first day of class has been changed.
C.Students are required to take the course.
D.The summer course has been cancele