Fact 1: Arteries generally carry oxygen-rich blood.

Fact 2: About O2, every living thing requires oxygen in order to live.

Given the two facts above, answer the question "Arteries generally carry blood full of" with the following options: 
- He
 - Au
 - O3
 - O2
 - DDT
 - Ni
 - CO2
 - gas


 

    O2     