单项选择题
A.metal particles loosened by wear
B.air when no air cleaners are used
C.condensation of water vapors
D.breakdown of the lubricating oil by dilution
单项选择题 The amount of fuel injected in a particular time, or degree, of crankshaft rotation is termed （）.
单项选择题 A crankshaft whose center of gravity coincides with its center line is said to be （）.
单项选择题 When centrifuging heavy fuel oil, an important factor to consider is the （） (1) flow rate (2) viscosity of the fuel oil