You are presented with the question "What can gas furnaces cause?" and the following answer choices: 
- matter vibrating
 - Pollution
 - rain
 - Stale air
 - condensation
 - emissions
 - suffocation
 - friction

Now knowing that carbon monoxide is a gas produced by furnaces and other devices that burn fuel and excessive accumulation build-up of carbon monoxide can cause suffocation, choose the best answer.


 

       suffocation  