单项选择题
Mechanical energy in transition is referred to as （）.
A.horsepower B.work C.heat D.velocity
单项选择题 If you change from a low pour point lubricant to a high pour point lubricant in a refrigeration system, （）.
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 （）.
