单项选择题
If the detergent type lubricating oil being used in a diesel engine is black, the oil （）
A.must be centrifuged B.must by filtered C.must be changed D.is holding finely dispersed carbon in suspension
单项选择题 Which of the following statements describes the results of excessive microbiological growths within a fuel system?（）
单项选择题 A well-lubricated bearing surface always appears（）
单项选择题 If the plunger or barrel of a fuel injection jerk pump becomes damaged,（）
