Fact 1: Oxygen is essential for cellular respiration for all aerobic organisms.

Fact 2: Cellular respiration is a requirement for life.

Given the two facts above, answer the question "Which is a requirement for life?" with the following options: 
- glucose
 - hydration
 - sunlight
 - scandium
 - recovery
 - oxygen
 - uranium
 - radon


 

      oxygen   