You are presented with the question "What can be done to water to remove harmful substances before drinking?" and the following answer choices: 
- evaporation
 - vaporization
 - Dipping a magnet into it
 - hydration
 - Mixing in heavy metals
 - Cooking
 - Boiling it
 - Adding purified water to it

Now knowing that treating water is used to remove harmful substances before drinking and boiling is the safest method of treating water, choose the best answer.


 

       Boiling it  