A)She has to take an exam on Friday.
B)She has to wait on Friday.
C)She has to stay at home on Friday.
D)She has to meet a friend on Friday.
原文：
M: Would you like to go on a tour with us on Friday?
F: I would enjoy that very much if I didn't have to take an exam on Saturday. I think I'd better stay home and study.
Q: Why didn't the woman accept the invitation?