单项选择题
The oil index of main engine should be controlled to prevent it from in heavy weather（）
A.over heat B.over speed C.over pressure D.over worn
单项选择题 A dry-type spark arrestor removes sparks from a diesel engine exhaust by（）
单项选择题 When the ship is going to enter into the harbor,（）
单项选择题 Which of the following represents the significance the fuel oil cetane number?（）
