The correct option is C Nitrogen dioxide
Acid rain is caused when sulphur dioxide, SO2 and nitrogen oxides (NO and NO2) are released into the atmosphere and react with water particles in the rainwater to form sulphuric acid and nitric acid. These acids fall on to the ground as acid rain. While a small portion of the gases that cause acid rain is from natural sources such as volcanoes, most of it comes from the burning of fossil fuels and industries.