单项选择题
If you change from a low pour point lubricant to a high pour point lubricant in a refrigeration system, （）.
A.compressor lubrication will be improved
B.oil will not leave the crankcase
C.compressor valves will be damaged
D.oil may congeal in the evaporator
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When a vessel is in dry-dock, the vessel’s engineers should （）.
A.examine the condition of the propeller
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Which of the listed devices would be installed at a control system air pressure reducing station?（）
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