单选题In conventional systems, the injection pressure（）, while it’s（）in common rail diesel engines.Afluctuates with the engine speed to some extent, independent of the engine speedBkeeps constant at all engine speed, dependent on the engine speed to some extentCkeeps constant at all engine speed, independent of the engine speedDis decided by the engine speed, constant at all engine speed
单选题
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
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