Answer: The correct answer is carbon.
Step-by-step explanation:
Combustion reaction is defined as the reaction in which a hydrocarbon burns in oxygen or reacts with oxygen gas to produce carbon dioxide and water molecule.
Fossil fuels are defined as the hydrocarbons which mainly contains coal, fuel oil, natural gas etc..
When fossil fuels are burned in air, it mainly releases carbon dioxide, sulfur dioxide, methane, nitrous oxide etc..
The major component released during the combustion of fossil fuels is carbon.
Hence, the correct answer is carbon.