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 （）.

If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.

The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.

An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.

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 （）.

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

Which of the following statements is correct concerning heat transfer?（）

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