The valve that prevents water from backing out of the boiler into the feed line is the（）. ["bottom-blow valve","skin valve","feed-check valve","feed-stop valve"]
对330～500kV线路，应按什么原则实现主保护的双重化？
每日营业前和营业结束后应由（）负责对网点服务场所进行大厅环境和安全检查。 ["支行行长","支行主管服务副行长","营业室负责人","大堂经理"]
画出WK-2型光控器外部接线图。
The mechanical exhaust valve operation system is replaced by（）in an electronic controlled ME engine. ["a system with a Hydraulic Power Supply (HPS) unit","a system with roller guides for exhaust valves","a system with an electronically controlled Alpha Lubricator","a system directly powered by electric motor"]
330～500kV线路的后备保护应按什么原则装设？
