You are presented with the question "What enters the atmosphere when coal, oil, and natural gas is burned?" and the following answer choices: 
- Heat
 - toxins
 - Cars
 - Gas
 - h2o
 - tar
 - Carbon
 - energy

Now knowing that burning fossil fuels increases the carbon in the atmosphere and carbon dioxide is produced by the burning of fossil fuels such as coal, oil and natural gas, choose the best answer.


 

       Carbon  