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

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

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

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

（）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（）

One of the reasons that cause oil flowed from sludge outlet of a self-cleaning separator is（）

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

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.

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