Fact 1: Acar engine usually converts gasoline into motion and heat through combustion.

Fact 2: Oxygen acts as an aid to combustion.

Given the two facts above, answer the question "What acts as an aid to a car engine converting gasoline into motion and heat?" with the following options: 
- Energy.
 - oxygen
 - nitrogen
 - helium
 - argon
 - energy
 - burning
 - sugar


 

  oxygen       