英译汉：gearbox ratio

1、Why a gearbox is needed in a ship driv

Why a gearbox is needed in a ship driven by a medium-speed diesel engine?（）ATo reduce the main engine speedBTo increase the main engine speedCTo govern the main engine speedDTo fix the propeller shaft

2、Concentration ratio集中度

Concentration ratio集中度

3、DNB比 DNB ratio（DNBR）

DNB比 DNB ratio（DNBR）

4、P/O比(P/O ratio)

P/O比(P/O ratio)

5、英译汉：gearbox

英译汉：gearbox

6、抚养比(dependency ratio)

抚养比(dependency ratio)