What is the primary cause of acid rain?

The primary cause of acid rain is sulfur dioxide emissions. When sulfur dioxide (SO2) is released into the atmosphere, often from burning fossil fuels such as coal and oil in power plants and industrial processes, it can react with water vapor, oxygen, and other chemicals to form sulfuric acid (H2SO4). This acid can then mix with rain, resulting in acid rain.

Acid rain has significant environmental impacts, including damage to aquatic ecosystems, forests, and soils, and it can harm buildings and infrastructure. While nitrogen oxides also play a role in producing acid rain by forming nitric acid, sulfur dioxide is generally considered the more prevalent and significant contributor, especially in regions where coal is a major energy source.

The other options, such as carbon dioxide and volatile organic compounds, do not directly lead to the formation of acid rain; instead, they contribute to other environmental issues, which is why they are not the correct choice in this context.