听力原文:W: Hello, this is Dr. Gray's office. We're calling to remind you of your 4:15 app
M: Oh, thanks. It's a good thing that you called. I thought it was 4:15 today.
Q: What does the man mean?
(16)
A.He was confused about the date of the appointment.
B.He's glad he called the doctor.
C.He can't come until 4:15.
D.He feels happy that he can change the appointment.