Fact 1: Burning fossil fuels increases the carbon in the atmosphere.

Fact 2: Carbon dioxide is produced by the burning of fossil fuels such as coal, oil and natural gas.

Given the two facts above, answer the question "What enters the atmosphere when coal, oil, and natural gas is burned?" with the following options: 
- Heat
 - toxins
 - Cars
 - Gas
 - h2o
 - tar
 - Carbon
 - energy


 

       Carbon  