Fact 1: Using a gasoline engine requires burning gasoline.

Fact 2: Gasoline ignites easily and burns vigorously.

Given the two facts above, answer the question "using a gasoline engine requires what?" with the following options: 
- electricity
 - no ignition
 - carbon dioxide
 - easy ignition
 - difficult ignition
 - no gasoline
 - hydrogen and oxygen
 - adding heat


 

    easy ignition     