You are presented with the question "A car engine uses what to aid in combustion?" and the following answer choices: 
- carbon dioxide
 - electricity
 - organic molecules
 - thrust
 - hydrocarbons
 - a hydraulic system
 - kinetic energy
 - fossil fuels

Now knowing that acar engine usually converts gasoline into motion and heat through combustion and gasoline is made up of hydrocarbons, choose the best answer.


 

     hydrocarbons    