The correct answer is B) reduced by finer atomization. Finer atomization of the fuel oil results in smaller fuel droplets, which have a larger surface area-to-volume ratio. This allows for more efficient mixing and vaporization of the fuel in the cylinder, reducing the likelihood of fuel oil penetrating the cylinder walls. Poorer atomization leads to larger fuel droplets, which are more likely to impinge on the cylinder walls, resulting in fuel oil penetration. The other options are incorrect: A) air turbulence affects the combustion process but not specifically fuel oil penetration, C) finer atomization reduces, not increases, fuel oil penetration, and D) the precombustion chamber system is not relevant to the question, which is focused on direct injection diesel engines.