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

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 （）.

A salinity indicator is used to determine the （）.

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

Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）

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

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

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

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