Which of the following is NOT one of the three major pollutants released by fossil fuels after combustion?

The correct answer is based on the classification of the major pollutants commonly associated with fossil fuel combustion. Carbon monoxide, nitrogen oxides, and hydrocarbons are all significant pollutants emitted during the combustion of fossil fuels. These pollutants contribute to various environmental and health issues, including smog formation and respiratory problems.

Sulfur dioxide, while a well-known pollutant produced by fossil fuel combustion—especially from the burning of coal and oil—is not always categorized alongside the primary group associated with everyday emissions from most fossil-fuel combustion sources. Instead, it is often discussed in the context of specific types of fuels or industrial processes rather than as one of the three major pollutants typically highlighted in standard emissions discussions.

Understanding the differences in pollutant types can help clarify why sulfur dioxide does not fit within the most frequently referenced three. In pollution regulation and discussion, it's common to focus on the latter three pollutants, making their identification crucial for those studying emissions and environmental impact.