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

A pressure drop through the refrigerant liquid line may cause （）.

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

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

The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.

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

Which of the following statements is correct concerning heat transfer?（）

A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.

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（）.