Fact 1: Acid rain has a negative impact on water quality.

Fact 2: Sulfur dioxide causes acid rain.

Given the two facts above, answer the question "What has a negative impact on water quality?" with the following options: 
- Reverse osmosis
 - fossil fuels
 - Fresh water
 - Carbon filter
 - chlorofluorocarbons
 - Sulfur dioxide
 - Pollution
 - harmful substances


 

      Sulfur dioxide   