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

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

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

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

A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.

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

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

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

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

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