单项选择题
In an internal combustion engine, which of the devices listed will force the compression rings to seal the compression gases in the space above the piston?（）
A.Used of bimetallic piston rings B.Ring gap pre-tensioning C.Thermal increase in ring-end clearance D.Gas pressure acting against the back of the ring
单项选择题 If the detergent type lubricating oil being used in a diesel engine is black, the oil （）
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（）
