The output volume of a positive fixed displacement pump can be changed only by （）.

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

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

When the steering gear is in operation, you should （）.

Thermostatic expansion valves can be adjusted for （）.

A salinity indicator is used to determine the （）.

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

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

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

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