单项选择题
Why a gearbox is needed in a ship driven by a medium-speed diesel engine?（）
A.To reduce the main engine speed B.To increase the main engine speed C.To govern the main engine speed D.To fix the propeller shaft
单项选择题 Which one is not true?（）
单项选择题 The displacement of a ship is to the total weight, all told, of the relevant loaded ship（）
单项选择题 When a ship in loaded condition floats at arbitrary water line, its displacement is to the relevant mass of water displaced by the ship（）
