Which of the listed pumps is NOT a positive displacement pump?（）

Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）

Low compressor head pressure in a refrigeration system can be caused by（）.

If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.

The general purpose of a heat exchanger is to （）.

The major source of chemical contaminants in hydraulic fluid is （）.

If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.

On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.

A salinity indicator is used to determine the （）.

The usual symptoms of cavitation in a centrifugal pump is （）.