Fact 1: Using a gasoline engine requires burning gasoline.

Fact 2: For every one gallon of gasoline an engine burns, one gallon of water is produced as a by-product.

Given the two facts above, answer the question "What is NOT a byproduct of using a gasoline engine?" with the following options: 
- chickenpox
 - carbon dioxide
 - carcinogens
 - Collagen
 - water
 - warmth
 - loose dirt
 - uranium


 

        uranium 