石油着火属于（）.
A.甲类火
B.乙类火
C.丙类火
参考答案：B
变量L的值为-8，则-L^2的值为（ ）。
A．64
B．-64
C．16
D．-16
John opened the door. There _____ he had never seen before. [ ]
A. a girl did stand
B. a girl stood
C. did a girl stand
D. stood a girl
