（）are used to digest the sewage to produce innocuous sludge in a biological sewage treatment plant.

The shipboard oil pollution emergency plan will be invalid after （）

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

A purge recovery system is used in a centrifugal air conditioning or refrigeration system to （）

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

By comparing the exhaust gas temperature of each cylinder, the operator can determine if the load is balanced throughout the engine. The device most commonly used is a（）

If separating effect is not good, which measure should be taken （）

Thermostatic steam pressure reducing valves are used in the fuel oil service system to control the（）

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

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