The correct answer is D) produce heavy black smoke at any load condition. When the temperature of the fuel oil entering the atomizer is too low, the fuel will not atomize properly. This results in incomplete combustion, which leads to the production of heavy black smoke regardless of the load condition. The low fuel temperature makes it difficult for the fuel to break up into fine droplets, preventing efficient mixing with air for complete combustion. The other options are incorrect because: A) increased fuel flow would not resolve the issue of poor atomization, B) white smoke is typically associated with incomplete combustion of lighter distillate fuels, not heavier fuel oils, and C) excess air alone cannot compensate for the poor atomization caused by low fuel temperature.