You are presented with the question "Biomes that have suffered mainly from pollution have water that contains little or no what?" and the following answer choices: 
- Toxins
 - CO 2
 - liquid
 - salt
 - Lead
 - Carbon
 - Acids
 - sulfur

Now knowing that freshwater biomes have water that contains little or no salt and freshwater biomes have suffered mainly from pollution, choose the best answer.


 

    salt     