Fact 1: Treating water is used to remove harmful substances before drinking.

Fact 2: Ordinary tap water can be full of harmful substances like chlorine, pesticides and heavy metals.

Given the two facts above, answer the question "What does treating water remove before drinking it?" with the following options: 
- direct damage to the lungs
 - h2o
 - an area swollen with pus
 - chlorine, pesticides, heavy metals
 - molecules
 - vapor
 - Mutagenic chemicals
 - nonliving organic matter


 

    chlorine, pesticides, heavy metals     