You are presented with the question "using a gasoline engine requires what?" and the following answer choices: 
- electricity
 - no ignition
 - carbon dioxide
 - easy ignition
 - difficult ignition
 - no gasoline
 - hydrogen and oxygen
 - adding heat

Now knowing that using a gasoline engine requires burning gasoline and gasoline ignites easily and burns vigorously, choose the best answer.


 

    easy ignition     