Https://www.ncbi.nlm.nih.gov/pubmed/8300084
This might help
Because of its ability to form large complex and diverse molecules
Animals and plants need to get rid of carbon dioxide gas through a process called respiration. Carbon moves from fossil fuels to the atmosphere when fuels are burned. When humans burn fossil fuels to power factories, power plants, cars and trucks, most of the carbon quickly enters the atmosphere as carbon dioxide gas.
I believe the correct answer is a. mutations.