to remove harmful substances to add color to increase its supply to decrease its temperature
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Water is often put through a treatment system before it is used in homes as drinking water. Which is the most likely reason water is treated before people drink it?
Possibilities:
- to remove harmful substances
- to add color
- to increase its supply
- to decrease its temperature

to remove harmful substances