（）connectors hold best if a wire is accidentally pulled or a connection becomes loose.

When does auxiliary burner of incinerator put into operation? （）Ⅰ. start incinerator when it is coldⅡ. the sludge for dealing with is littleⅢ. the sludge for dealing with is largeⅣ. the water and impurity in sludge are too muchⅤ. the temperature in incinerator is lowⅥ. dealing with little solid rubbish

Which of the diesel engine components listed increase air density and helps to improve engine operating efficiency?（）

Engine parameters shall be corresponded to NOx Technical Files. This is required by （）

If two A.C.generators are to be operated in parallel, the load is distributed evenly by（）

Refrigerant entering the compressor of a refrigeration system should be in which of the following conditions?（）

（） is not installed on the main switchboar.

The condensers located in various stages of a flash evaporator are cooled by（）

During the diesel engine running, the water level of F.W expansion tank should normally kept in the （） level of glass tube.

For a given exhaust gas boiler, what is the quantity of its evaporation mainly determined?（）