由于变频器具有软启动、无冲击的特性，所以空气开关可以按变频器的（）选择。
A、容量
B、电流
C、功率
D、电压
参考答案：A
Nicolaus Copernicus’ discovery about the universe is ______, which ______later achievements in astronomy science. [ ]
A. ambitious; gave birth to
B. enthusiastic; resulted in
C. obvious; resulted in
D. revolutionary; led to
一电池外电路断开时的路端电压为3V，接上8Ω的负载电阻后路端电压降为2.4V，则可以判定电池的电动势E和内电阻r为（）
A.E=2.4V，r=1Ω
B.E=3V，r=2Ω
C.E=2.4V，r=2Ω
D.E=3V，r=1Ω
