单项选择题
A grease gun is generally used to lubricate a （）.
A.condensate pump ball bearing B.main shaft bearing C.main turbine bearing D.diesel engine wrist pin bearing
单项选择题 Thermostatic expansion valves can be adjusted for （）.
单项选择题 The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
单项选择题 The major source of chemical contaminants in hydraulic fluid is （）.
