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

An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.

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

If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.

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

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

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

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

An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.

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