单项选择题
A diesel engine piston ring face is in direct contact with the （）.
A.top of the ring groove B.cylinder liner oil film C.bottom of the ring groove D.back of the ring groove
单项选择题 If the water level dropped rapidly in the expansion tank of a closed diesel engine cooling water system, you should suspect a （）.
单项选择题 In a simple mechanical governor, the （）.
单项选择题 The ability of the governor to prevent fluctuations in engine speed is termed （）.
