电能质量通常用( )项指标来衡量。
A．电压和频率
B．功率因数和电流
C．用电量和电压
D．供电时间和频率
参考答案：A
— What time is it?
— Sorry, I don't know. I _____ a watch. [ ]
A. have
B. don't have
C. doesn't have
一题多解、一物多用等体现了（）思维。
A.发散
B.收敛
C.逆向
D.正向
