One cause of high head pressure occurring in a refrigeration system can be （）.

An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.

The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.

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

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

A salinity indicator is used to determine the （）.

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

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

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

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