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

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

Which of the listed pumps is NOT a positive displacement pump?（）

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

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

If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.

An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.

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

The general purpose of a heat exchanger is to （）.

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