单项选择题 A two-stroke diesel engine exhaust temperature will be lower than a four-stroke diesel engine of the same displacement because the （） (1) scavenging air is cooling the exhaust gases (2) exhaust cycle time is longer

单项选择题 If the chemical analysis of a lube oil sample taken from a diesel engine indicates an increased neutralization number, the （）.

单项选择题 When an auxiliary boiler is panting and emitting black smoke, you should （）.