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

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

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

The main purpose of port State control is not to（）

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

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

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

To shut down a diesel engine after it exceeds the set maximum speed，which type of device listed should be used?（）

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

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