问题
The light in his office is still on. Do you know _______?—To prepare for the material(材料) the meeting will need tomorrow, I think.
A:if he works hard
B:why he stays up so late
C:why is he so busy
D:when he will stop working
B:why he stays up so late
C:why is he so busy
D:when he will stop working
正确答案是：
