单项选择题 Visual inspection of chrome-plated piston compression rings reveals a black ring face at the position of the cylinder liner portsThis condition indicates a ring which（）

单项选择题 A bright shiny appearance of the sealing surfaces on diesel engine compression rings indicates（）

单项选择题 Following the failure of one turbocharger on a large, crosshead, main propulsion diesel engine, fitted with multiple turbochargers, which of the following actions should be taken prior to further operation of the engine? （）