单项选择题
Properties of a good refrigeration oil include（）
A.low wax content B.high pour point C.high viscosity D.all of the above
单项选择题 Proper filtering and straining of diesel fuel is important because the（）
单项选择题 Which factor determines the ring dam size for a fuel oil, tubular bowl type, centrifugal purifier?（）
单项选择题 If the bowl of a disk type centrifugal purifier when operated as a separator is not primed, the（）
