单项选择题

M: I hope that Mr. Wang will be in the office.
W: Well he usually works from 8:00 a.m. to 5:00 p. m... On Saturdays and Sundays, he works from 9:00 a.m. to 12:00 noon.

When will Mr. Wang begin to work on weekends()

A.5p.m. 
B.12noon. 
C.8a.m. 
D.9a.m.