Acid rain has a negative impact on water quality, and acid rain has a pH below 5.6. Given these facts, what has a negative impact on water quality among the following options:
- rain
 - harmful substances
 - rain below 5.6 pH
 - sleet
 - fossil fuels
 - Burning fuel and air
 - snow
 - decaying trees


 

   rain below 5.6 pH      