Fact 1: Freshwater biomes have water that contains little or no salt.

Fact 2: Freshwater biomes have suffered mainly from pollution.

Given the two facts above, answer the question "Biomes that have suffered mainly from pollution have water that contains little or no what?" with the following options: 
- Toxins
 - CO 2
 - liquid
 - salt
 - Lead
 - Carbon
 - Acids
 - sulfur


 

    salt     