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

Fact 2: An inevitable byproduct of burning fossil fuels is carbon dioxide.

Given the two facts above, answer the question "what is a byproduct of fossil fuels?" with the following options: 
- heat
 - sugar
 - energy
 - Cars
 - carbon
 - bacteria
 - tar
 - Pollution


 

     carbon    