单项选择题
A.quality of air filtration
B.effectiveness of lubrication
C.type of fuel used
D.all of the above
单项选择题 In diesel engineering practice, the term used to express the ignition quality of a particular fuel is（）
单项选择题 The cetane number rates fuels for diesel engines according to its （）
单项选择题 Diesel engine starting difficulties due to cold intake air temperatures, can be overcome by using a/an（）