电炉炉膛分为（）、（）、还原区（或坩埚区）、弧光（电弧）区、（）和假炉底。
参考答案：预热区；烧结区；熔池区
Everybody needs calcium, but it is quite possible for a similar person to be totally healthy by eating only________.
A．as half much
B．as much half
C．half as much as
D．half as much
高压断路器校验其热稳定性与动稳定性所用的电量分别是系统的（）。
A．三相短路电流稳态值
B．三相短路电流冲击值
C．三相短路电流暂态值
D．三相短路电流最小值
