The correct answer is: B. 40-50% of air pollution.
Mobile combustion is the burning of fuel in vehicles, such as cars, trucks, and buses. It is a major source of air pollution, accounting for 40-50% of air pollution in the United States. Mobile combustion emits a variety of pollutants, including particulate matter, nitrogen oxides, and volatile organic compounds. These pollutants can cause a variety of health problems, including respiratory problems, heart disease, and cancer.
Option A is incorrect because mobile combustion accounts for 40-50% of air pollution, not 10-20%.
Option C is incorrect because mobile combustion accounts for 40-50% of air pollution, not 50-60%.
Option D is incorrect because mobile combustion accounts for 40-50% of air pollution, not 5-10%.