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

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

Which of the following items don’t belong to dock repair works?（）

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

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

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

To proceed to the assistance of a ship in distress is（）

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

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

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