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

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

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

“Insufficiency of manning or insufficiency of certification of seafarers” is an identification of a（）

The additional mark （）in the Classification Certificate for Machinery means propulsion apparatus is remotely controlled on the navigating bridge control station, and engine assembly control station is unmanned periodically.

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

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

The flash point of a residual fuel oil should be used to determine the highest temperature to which oil may be heated（）

Which one is NOT the ‘clear grounds’ for a more detailed inspection?（）

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