Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.

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

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

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

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

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

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

On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.

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

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