You are presented with the question "What happens when a fuel burns incompletely?" and the following answer choices: 
- Carbon monoxide disappears
 - direct damage to the lungs
 - deadly and devastating
 - Carbon monoxide is created
 - retaining heat
 - Oxygen increases
 - permineralization
 - It's recycled

Now knowing that carbon monoxide is a gas produced by furnaces and other devices that burn fuel and any fuel that is incompletely burned produces carbon monoxide, a colorless, odorless gas, choose the best answer.


 

    Carbon monoxide is created     