单选题Air compressor cylinder un-loaders enable the compressor to （）.Avary their speed according to temperature and loadBstart and come up to speed before air compression beginsCchange speed according to overload demandsDreduce compressed air charge density
单选题
Air compressor cylinder un-loaders enable the compressor to （）.
A
vary their speed according to temperature and load
B
start and come up to speed before air compression begins
C
change speed according to overload demands
D
reduce compressed air charge density
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