配置备用电源自动投入装置,对电网带来的好处为()。
A.提高供电可靠性
B.降低造价,节省投资
C.继电保护配置简单化
D.简化电网一次接线
参考答案:A, B, D
Our school is having a sports meeting. Someone _____ here already. [ ]
A. arrived
B. have arrived
C. has arrived
管道外部加保温层的目的是()管道的热阻,()热量的传递