You are presented with the question "What is treating water used to remove before drinking?" and the following answer choices: 
- arsenic
 - air
 - cellulose
 - chemicals
 - Collagen
 - loose dirt
 - water vapor
 - ice

Now knowing that treating water is used to remove harmful substances before drinking and arsenic, a naturally occurring substance, contaminates water sources in many countries, choose the best answer.


 

 arsenic        