单选题The closing of the exhaust valves used on a modern, large, low-speed, main propulsion diesel engine may be directly provided by （）.Alarge conical springsBcompressed air pressureChydraulic pressureDexhaust gas pressure
单选题
The closing of the exhaust valves used on a modern, large, low-speed, main propulsion diesel engine may be directly provided by （）.
A
large conical springs
B
compressed air pressure
C
hydraulic pressure
D
exhaust gas pressure
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