单项选择题
A.leaky exhaust valve
B.increased scavenging air temperature
C.engine cylinders not scavenged sufficiently
D.water in the fuel oil
单项选择题 Fresh water is used for the cooling of cylinder jackets and （） of the marine diesel engine.
单项选择题 Four strokes consist of suction, compression, （） and exhaust stroke.
单项选择题 For one or two types of engine,the piston and rod can be withdrawn downwards from the cylinder into the crankcase and then out through （）.