SF6断路器的缺点有哪些？
参考答案：
要求加工精度高，密封性要求高，对水分和气体的检测控制要求严格。
---Nowadays children are bearing too heavy a learning burden.
---______. So much homework do they have to do that they almost have no time for other activities.
A．So what?
B．It cannot be better
C．Good idea
D．I cannot agree more
一次正常排精量为（）
A.<5ml
B.<4ml
C.2～6ml
D.<2ml
E.>6ml
