提高功率因数的意义在于（）。
A.防止设备损坏
B.提高电源电流
C.提高供电设备利用率
D.提高电源电压
参考答案：C
- How was the performance last night?
- It was so good. Though it ＿＿＿＿＿＿ nearly four hours, few people left early.
A．covered
B．reached
C．lasted
D．played
什么称为饱和蒸汽压？
