You are presented with the question "What has a negative impact on water quality?" and the following answer choices: 
- rain
 - harmful substances
 - rain below 5.6 pH
 - sleet
 - fossil fuels
 - Burning fuel and air
 - snow
 - decaying trees

Now knowing that acid rain has a negative impact on water quality and acid rain has a pH below 5.6, choose the best answer.


 

   rain below 5.6 pH      