Which gas is primarily released by burning fossil fuels?

• A. Carbon Dioxide
• B. Methane
• C. Nitrous Oxide
• D. Ozone

Answer: (A)

When fossil fuels burn, the carbon in the fuel combines with oxygen to form carbon dioxide, which is released in the largest amounts. This comes from the typical complete combustion of hydrocarbons, where fuel plus oxygen yields carbon dioxide and water; carbon dioxide tends to be far more abundant than other gaseous products. Methane can be released during fuel extraction and handling, and nitrous oxide can form in some high-temperature combustion, but their overall contributions are much smaller than CO2. Ozone is not directly produced by burning; it forms later in the atmosphere from reactions involving other pollutants and sunlight. So carbon dioxide is the main gas emitted when fossil fuels burn.