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
单项选择题 When a vessel is in dry-dock, the vessel’s engineers should （）.
单项选择题 Air line lubricators are used in compressed air systems to lubricate （）.
单项选择题 Which of the listed devices would be installed at a control system air pressure reducing station?（）
