单项选择题
In a diesel engine, offers the heat energy directly（）； works as working medium and changes the heat energy to mechanical energy（）
A.the burning of the fuel； medium shaft B.fuel spray； fresh air C.fuel； fuel spray D.the burning of the fuel； the burned gas mixture
单项选择题 A propeller, in order to operate efficiently, must rotate at a relatively （） speed.
单项选择题 Why a gearbox is needed in a ship driven by a medium-speed diesel engine?（）
单项选择题 Which one is not true?（）
