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

Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.

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

Thermostatic expansion valves can be adjusted for （）.

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

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 （）.

A pressure drop through the refrigerant liquid line may cause （）.

If the head pressure of a reciprocating refrigeration compressor is excessive, （）.

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

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