Alberta Boilers Safety Association (ABSA) Practice Test

The correct choice is sulphur dioxide. This gas is a significant contributor to acid rain because when it is released into the atmosphere, it can react with water vapor, oxygen, and other chemicals to produce sulfuric acid. When this acid falls to the ground as precipitation, it results in acid rain, which can have detrimental effects on the environment, including harming aquatic ecosystems, damaging forests, and corroding buildings and infrastructure.

Sulphur dioxide is mainly emitted from industrial processes, burning fossil fuels, and transportation. Its role in the formation of acid rain is well-documented and is a primary focus in environmental regulations aimed at reducing air pollutants.

While nitrogen dioxide also contributes to acid rain formation by producing nitric acid during similar atmospheric reactions, sulphur dioxide is recognized as a more significant contributor overall. Methane and carbon monoxide vary considerably in their environmental impacts but are not directly associated with acid rain formation. Methane primarily affects global warming as a potent greenhouse gas, and carbon monoxide is more related to air pollution and health issues than acid rain.