单选题Exhaust valve openings in a diesel engine cylinder head are made as large as practical to （）Aincrease back pressure during the exhaust processBfacilitate periodic replacement of the valvesCreduce the pumping loss associated with scavengingDreduce tension on valve springs
单选题
Exhaust valve openings in a diesel engine cylinder head are made as large as practical to （）
A
increase back pressure during the exhaust process
B
facilitate periodic replacement of the valves
C
reduce the pumping loss associated with scavenging
D
reduce tension on valve springs
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