Answer
B. sulfur dioxide released from a coal-fired power plant.
Explanation
Power plants release the majority of sulfur dioxide and much of the nitrogen oxides when they burn fossil fuels, such as coal, to produce electricity. In addition, the exhaust from cars, trucks, and buses releases nitrogen oxides and sulfur dioxide into the air. These pollutants cause acid rain.
Therefore, what is directly responsible for acid rain is:
B. sulfur dioxide released from a coal-fired power plant.
