A.examine the condition of the propellerB.chip and pain……

单项选择题Air line lubricators are used in compressed air systems to lubricate （）.

A.the suction and discharge valves
B.tools and equipment served by compressed air
C.air line reducing valves
D.all of the above

单项选择题Which of the listed devices would be installed at a control system air pressure reducing station?（）

A.Moisture separator
B.Vacuum breaker
C.Lubricator
D.Non-return valve

单项选择题Power is defined as the （）.

A.rate of doing work
B.amount of force needed to overcome friction
C.amount of work accomplished
D.distance through which an object is moved

单项选择题To correct the condition of slugging and flooding back in a refrigeration system, it may be necessary to （）.

A.re-adjust the discharge pressure
B.clean the expansion valve screen
C.add refrigerant
D.adjust the expansion valve

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

A.splash method
B.mechanical force feed lubricators
C.detached sump method
D.internal cooling passages in the crankshafts and connecting rods