You are presented with the question "what can cause the ph of soil to decrease?" and the following answer choices: 
- Greenhouse gasses
 - contamination
 - fossil fuels
 - chlorofluorocarbons
 - incinerated mercury
 - harmful substances
 - Greenhouse gases
 - Temperature

Now knowing that air pollution can cause the pH of soil to decrease and incinerated mercury pollutes the air, choose the best answer.


 

     incinerated mercury    