單項選擇題Although lube oils used in the main lubricating service systems should have a relatively high flash point to avoid ignition, they can create smoke and fire hazards when they （）.

A.are exposed to a vacuum
B.come in contact with extremely hot surfaces
C.are reduced in temperature to just above the pour point
D.become extremely agitated or aerated


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1.單項選擇題The viscosity of an oil is a measure of its （）.

A.weight
B.internal friction
C.demulsibility

2.單項選擇題The pour point of lubricating oils is affected the most by which of the following?（）

A.Extensive centrifuging
B.Wax content
C.Water content
D.Acid content

3.單項選擇題Which of the following statements is correct concerning the viscosity of lubricating oil?（）

A.Viscosity will increase as temperature increases
B.Viscosity is a measure of a fluid s internal resistance to flow
C.Viscosity will decrease as temperature decreases
D.Viscosity is not dependent on temperature

4.單項選擇題Under normal operating conditions, the rudder is hydraulically locked unless （）.

A.the manual trick wheel is engaged for steering
B.the variable stroke pump is off stroke
C.a rudder order is given by the control system
D.an electric power system failure occurs at the steering gear

5.單項選擇題Saltwater is typically provided to a refrigeration system to （）.

A.cool the expansion valve
B.prevent refrigerant superheating
C.condense the refrigerant gas
D.prevent motor overheating