The opening of an exhaust valve on a modem large low-speed main propulsion diesel engin

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The opening of an exhaust valve on a modem, large, low-speed, main propulsion diesel engine may be actuated by _____.

A.direct action of cam shaft

B.compressed air pressure

C.hydraulic “push rods”

D.direct action of the main piston moving down

请帮忙给出正确答案和分析,谢谢!

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