电气火灾的原因主要有()、()、()和()四种。
参考答案:短路;过负荷;接触电阻电火花;电弧
That rude boy ________ have rushed out of the classroom when Ms Green was giving a lecture, which
finally led to his being punished by the head teacher.[ ]
A.could
B.must
C.dare
D.should
简述低电压穿越(LVRT)。具体我国电网公司是如何规定的?