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

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（）

Diesel engine air start system check valves are opened by （）

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

The Port State Control officer may witness a fire drill carried out by the crew assigned to these duties on the（）

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

The treatment of the fuel oils involves storage, heating, filtering and（）

Flame failure in an automatically fired auxiliary boiler can from a/an （）

Cold weather starting of a diesel engine may be made easier by（）

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