-Why are you in such a hurry?    

-I was told that my mother had been sent to the hospital. I have to leave ________.[ ]

A．before long              

B．right now

C．from now on              

D．all the time

设计测试用例的方法有黑箱法和白箱法。以日方法中属于白箱法的是（）。

A．语句覆盖法

B．等价分类法

C．边缘值分析法

D．错误推测法