You are presented with the question "To ensure that water is safe to drink, harmful what are removed before drinking?" and the following answer choices: 
- leeches
 - seeds
 - toxins
 - currents
 - bacteria
 - substances
 - Roundworms
 - plants

Now knowing that treating water is used to remove harmful substances before drinking and to ensure that it is safe to drink water, treat it all the time, choose the best answer.


 

      substances   