Final answer:
The greatest amounts of nitrogen oxides (NOx) in the atmosphere are produced by transportation sources, fuel combustion in utility plants and industry, and denitrification in farm fields.
Step-by-step explanation:
Nationally, the greatest amounts of nitrogen oxides (NOx) in the atmosphere are produced by:
- Transportation sources (motor vehicles, aircraft, trains)
- Combustion of fuel in electrical utility plants and industry
- Denitrification in farm fields
The correct answer to the question would be D: I, II, and III. Transportation and industrial activities are well-known sources of NOx due to the combustion of fossil fuels. Additionally, NOx is also produced by agricultural practices through the process of denitrification, where nitrogen from fertilizers is converted back into nitrogen gas or into nitrous oxide, a potent greenhouse gas, contributing to the release of NOx into the environment.