单项选择题
A.the supply of normal air and removal of compressed air
B.the supply of fuel oil and combustion of the atomized oil
C.the supply of fresh air and removal of exhaust gases
D.the supply of fresh air and removal of the extra heat
单项选择题 “The use of a poor quality oil can lead to rapid deterioration of its properties with the resultant formation of deposits in the piston crown which in turn results in a considerable reduction in heat transfer with subsequent overheating and thermal cracking” According to this sentence, we can know that the principle reason of the overheating and thermal cracking is（）
单项选择题 Large crosshead type engine generally has two lubrication systems, a function performed only by crankcase oil system is（）
单项选择题 Large crosshead type engine generally has two lubrication systems, a function performed only by cylinder oil system is（）