Because it is believed to arise from plant & animal carcasses that have existed for hundreds of years before. All fossil fuel consisting of hydrocarbons and carbon dioxide when it is burnt out.
Because believed to arise from the remains of plants and animals that lived hundreds of years ago. All fossil fuels contain hydrocarbons And release carbon dioxide when burned.
Because is believed to arise from plant and animal live hundreds of years ago. Fossil fuels comprising hydrocarbon. And the carbon dioxide come out when burned.