Fact 1: Afire requires oxygen to burn.

Fact 2: Oxygen-enriched air is a fire hazard because the burning rate of combustible materials is increased.

Given the two facts above, answer the question "How do you increase the burn rate?" with the following options: 
- an electric stove
 - exercise
 - burn wet materials
 - friction
 - add more oxygen
 - decrease amount of fuel
 - a hydraulic system
 - decrease the oxygen


 

     add more oxygen    