客户因欠费被停电，在交清欠费后应在多长时间内恢复送电？
参考答案：
24小时以内。
-Why was professor Liu thundering in the classroom yesterday?
-A student's interrupting his speech ____ the burst of hisanger. [ ]
A. set up
B. set out
C. set about
D. set off
当下面哪一条成立时，称X→Y为平凡的函数依赖（）
A.
B.
C.
D.
