— Where ______________ the library?
— It's over there. [ ]
A. am
B. is
C. are
答案:B
高压侧电压为500kV的变压器,那些()可以引起变压器工作磁密度过高。
A、频率降低
B、电压降低
大多数高炉都用()种炉料冶炼。