You are presented with the question "What does an engine require burning?" and the following answer choices: 
- Time and energy
 - energy
 - wind
 - water
 - carbon dioxide
 - layers of fat
 - fossil fuels
 - sunlight

Now knowing that using a gasoline engine requires burning gasoline and fossil fuels include coal, oil, natural gas, and gasoline, choose the best answer.


 

       fossil fuels  