问题描述：
-The light in his room is still on.Do you know______?-In order to prepare for the coming exam.
A.if he works hard
B.why he stays up so late
C.why is he so busy
d.when he will stop working
A.if he works hard
B.why he stays up so late
C.why is he so busy
d.when he will stop working
问题解答：
我来补答展开全文阅读