Fact 1: Carbon monoxide is a gas produced by furnaces and other devices that burn fuel.

Fact 2: Carbon Monoxide Carbon monoxide is a health hazard.

Given the two facts above, answer the question "What are the affects of burning fuel on human health?" with the following options: 
- emissions
 - They aid lung health.
 - direct damage to the lungs
 - They are a hazard.
 - The affects are mildly healthy
 - The fuel burns clean.
 - Greenhouse gases
 - Global warming


 

    They are a hazard.     