单项选择题
Pitted reduction gear teeth having a deep blue color with evidence of overheating have been operated with （）
A.excessive speed B.improper warm-up C.extreme misalignment D.inadequate lubrication
单项选择题 Which of the listed substances can be satisfactorily removed from diesel fuel by centrifuging?（）
单项选择题 The amount of fuel delivered by a unit injector is controlled by the （）
单项选择题 Cast iron pistons used in large propulsion diesel engines are constructed with （）
