单项选择题
If the flame from combustion in the cylinder of a four-stroke engine past the piston into the space below, the accumulation of flammable mixture would be ignited, thus resulting in （）.
A.the crankcase explosion B.lifting of the cylinder safety valve C.a scavenge fire D.opening of the manhole
单项选择题 If the engine does start on air, but combustion does not immediately begin, the cause may not be （）.
单项选择题 If the engine does start on air, but combustion does not immediately begin, the cause may be （）.
单项选择题 If the engine does not start on air, it may be due to （）
