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

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

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

The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?（）

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

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

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

If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.

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

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