Question 211Motor Plants - 1st Asst/Chief

The correct answer is B) 5-7% by volume. This is the correct answer because the most severe crankcase explosions typically occur when the oil mist to air ratio is within the flammable range, which is around 5-7% by volume. At this ratio, the mixture of oil mist and air is most easily ignited, leading to the most violent and destructive crankcase explosions. The other options are less likely to result in the most severe crankcase explosions. Ratios below 5% or above 7% are either too lean or too rich to be as easily ignited and explosive.