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

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

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

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

When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.

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

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

Thermostatic expansion valves can be adjusted for （）.

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

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