单项选择题
A.the firing pressure in the cylinder
B.a metering helix inside the pump
C.varying the physical length of the plunger stroke
D.varying the clearance between the injector cam and the injector rocker arm
单项选择题 Which of the following should always be checked prior to starting a diesel engine?（）
单项选择题 An after-cooler installed between the turbocharger and the cylinder air inlet （）
单项选择题 Proper lubrication of the main bearings is more easily obtained in a single acting, four-stroke/cycle diesel engine than in a tow-stroke/cycle diesel engine because（）.