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

Fact 2: The atmosphere is mostly carbon dioxide .

Given the two facts above, answer the question "What is the increased by burning fossil fuels?" with the following options: 
- fossils
 - Pollution
 - carbon dioxide
 - ions
 - Greenhouse gases
 - kinetic energy
 - air
 - heat energy


 

   carbon dioxide      