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

Fact 2: Global warming is caused by carbon dioxide trapped in the atmosphere.

Given the two facts above, answer the question "What kind of fuel use adds the most to global warming?" with the following options: 
- elbow grease
 - vehicles
 - fossil
 - Pollution
 - engines
 - Cars
 - hydroelectricity
 - solar energy


 

   fossil      