Automobile emissions are a significant source of air pollutants, and cars over five years old typically generate significantly greater amounts of pollutants than newer cars. In Torinia, which has recently built its first automobile manufacturing plant, most cars are over five years old. Aiming to boost Torinia' s economy and reduce air pollution, the government plans to introduce incentives for Torinians to scrap their old cars every five years and replace them with new ones. Which of the following, if true, most seriously undermines the likelihood that the planned incentives, if implemented, will achieve both of the cited aims? ['Without the implementation of the planned incentives, most Torinians who own an old car would be unlikely to buy a new car.', 'The manufacture and the scrapping of cars each generate significant amounts of air pollutants.', 'The largest source of atmospheric pollutants in Torinia is not automobile emissions, but emissions from power plants.', "Torinia's automobile plant manufactures car models that typically generate smaller amounts of air pollutants than most similarly sized car models manufactured elsewhere."]