Fossil fuels, they are natural fuels (because they are made of living organisms)
A. Human Activity
"According to the National Climate Assessment, human influences are the number one cause of global warming, especially the carbon pollution we cause by burning fossil fuels and the pollution-capturing we prevent by destroying forests. The carbon dioxide, methane, soot, and other pollutants we release into the atmosphere act like a blanket, trapping the sun's heat and causing the planet to warm. Evidence shows that 2000 to 2009 was hotter than any other decade in at least the past 1,300 years<span>. This warming is altering the earth's climate system, including its land, atmosphere, oceans, and ice, in far-reaching ways."
https://www.nrdc.org/stories/are-effects-global-warming-really-bad
Hope this helps!</span>
Explanation:
Natural materials are those that are found in nature and have not been made by humans. By comparison, synthetic materials are man-made and cannot be found in nature. Synthetic products are usually created in laboratories by mixing different chemicals, or prepared compounds and substances made in a laboratory.