单项选择题

M: How about seeing a film this evening
W: When
M: It begins at 7: 15. We’d better get there at 6:50.
W: Oh, sorry. My mother will leave for London this evening. I’m seeing her off at 7: 00.

When will the woman’s mother leave for London()

A. 7: 15.
B. 7:00.
C. 6: 50.