单项选择题
A.fluctuates with the engine speed to some extent, independent of the engine speed
B.keeps constant at all engine speed, dependent on the engine speed to some extent
C.keeps constant at all engine speed, independent of the engine speed
D.is decided by the engine speed, constant at all engine speed
单项选择题 The difference between Fixed pitch propeller (FPP) and Controllable pitch propeller (CPP) is in that（）
单项选择题 The propeller consists of a （）with several blades of helicoidal form attached to it.
单项选择题 Oil pressure in the lubrication system is（）than the static sea water head to ensure that sea water cannot enter the sterntube in the event of seal failure.