On small, low pressure, air compressors, the cylinders are usually lubricated by the （）.

单项选择题While troubleshooting a refrigeration system for low head pressure, liquid refrigerant flooding back from the evaporator is determined to be the causeIt may be necessary to （）.

A.change the expansion valve adjustment
B.readjust the water regulating valve to increase the flow of water
C.purge air from the condenser
D.clean the waterside of the condenser

单项选择题Air trapped in the hydraulic fluid of a steering system should be indicated by （）.

A.the pump over-speeding
B.an improper rudder response
C.bubbles in the sight glass
D.ram relief valves lifting

单项选择题Overgreasing of ball bearings installed on pumps will result in （）.

A.smoother pump operation
B.overheating of the bearing
C.reduced corrosion in the bearing
D.increased pump capacity

单项选择题The energy associated with molecules is known as （）.

A.kinetic energy
B.potential energy
C.mechanical energy
D.thermal energy

单项选择题“Flooding back” is a condition where the liquid refrigerant （）.

A.vaporizes in the condenser
B.reaches the compressor through the suction line
C.flashes in the liquid line
D.condenses in the receiver