单项选择题
Turbocharged four-stroke/cycle diesel engines utilize valve overlap for（）.
A.improving cylinder scavenging B.preheating the combustion chamber C.reducing air charge density D.preventing valve wear
单项选择题 Operating a propulsion diesel engine at less than 30% of designed normal load for prolonged periods will result in （）.
单项选择题 A dirty fuel oil filter element can be detected by （）
单项选择题 The major cause of fuel pump and injection system problems is （）
