A salinity indicator is used to determine the （）.

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

Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.

If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.

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

The output volume of a positive fixed displacement pump can be changed only by （）.

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

A grease gun is generally used to lubricate a （）.

The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.

The rate of heat transfer from a hot region to a cold region is affected most by the （）.