Which of the following gases is primarily responsible for acid rain?

The primary gas responsible for acid rain is sulfur dioxide. When sulfur dioxide is released into the atmosphere, typically from the burning of fossil fuels and other industrial processes, it can react with water vapor, oxygen, and other compounds in the atmosphere to form sulfuric acid. This process leads to the formation of acidic precipitation, commonly known as acid rain.

Acid rain can cause significant environmental damage, including the acidification of lakes and streams, harming aquatic life, and damaging forests and soil, which can lead to reduced plant growth and biodiversity. The contribution of sulfur dioxide to acid rain highlights the importance of controlling emissions from industrial sources as a means of protecting the environment.

While nitrogen dioxide can also contribute to acid rain, it primarily forms nitric acid. Carbon monoxide and methane are not significant contributors to acid rain formation, as they do not directly lead to the production of acids that can dissolve in precipitation. Therefore, sulfur dioxide is identified specifically as the main gas responsible for this environmental issue.