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 （）.

A salinity indicator is used to determine the （）.

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

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

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

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

Thermostatic expansion valves can be adjusted for （）.

Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）

The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?（）