Which one of the following is NOT a greenhouse gas produced by burning fossil fuels?

The correct answer is oxygen. When fossil fuels are burned, they undergo a chemical reaction that primarily releases carbon dioxide, methane, and nitrous oxide, all of which are greenhouse gases. These gases contribute to the greenhouse effect, trapping heat in the Earth's atmosphere and leading to global warming.

Oxygen, on the other hand, is not produced as a result of burning fossil fuels. In fact, it is consumed during the combustion process because fossil fuels require oxygen to burn. The main products are carbon dioxide and water vapor, along with other compounds depending on the fuel type and combustion conditions. Therefore, while carbon dioxide, methane, and nitrous oxide enhance the greenhouse effect, oxygen does not fit into this category as it does not contribute to climate change in the same way.