单项选择题

Office Hours
I am becoming increasingly concerned about the punctuality of certain members of staff and would like to remind all staff that our office hours are from 9:00am until 4:30pm; morning and afternoon breaks are 15 minutes each, and that the lunch break ends at 1:30pm. Please note that this time-table must be stuck to by all members of staff.
Miss Treadgold
Office Manager
12 April 2010
The staff are supposed to start work ______.

A. at 1:30 in the morning
B. at 4:30 in the morning
C. at 8:00 in the morning
D. at 9:00 in the morning