In common rail engines, the fuel is（） before is injected into the cylinders.

单项选择题In conventional systems, the injection pressure（）, while it’s（）in common rail diesel engines.

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（）

A.for FP, once fitted, the position of the blades can also be changed in operation
B.for CP, once fitted, the position of the blades can also be changed in operation
C.the CP type has a relatively smaller hub compared with the FP propellers
D.the FP type has a relatively larger hub compared with the CP propellers

单项选择题The propeller consists of a （）with several blades of helicoidal form attached to it.

A.shaft
B.boss
C.wheel
D.lever

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.

A.higher
B.lower
C.very higher
D.very lower

单项选择题（）is used to prevent the entry of sea water to the machinery space.

A.A special sealing gland
B.Propeller
C.Tailshaft
D.Sterntube bearing