一级负荷中特别重要的负荷，除由_______个独立电源供电外，还须备有_______ ，并严禁其他负荷接入。

在三相短路电流常用的计算方法中，______适用于多个电压等级的供电系统。

All people, whether they be rich or poor, strong or weak, privileged or deprived，are interdependent, and _______ the common task of seeking to achieve mankinds full potential

Many boys enjoy _______ football, basketball or baseball

－ What does the sign over there read － “No person ________ smoke or carry a lighted cigarette, cigar or pipe in this area”

Which do you think is ________, health or wealth？

编制数量指标指数时,一般将__做为同度量因素,并固定在__,编制质量指标指数时,一般将__做为同度量因素,并固定在__。

29．__________ when you are on the bus or bike．

Which do you think is _________________important, health or wealth?

Duty is an act or a course of action that people __________you to take by social customs, law or religion.

电机从供电方式分类可以分为 ___ 和___ 两大类。

提高供电电路的功率因数，下列说法正确的是________。