Answer: Option (C) is the correct answer.
Step-by-step explanation:
Water is a natural resource of water and life without water is not possible. As it is one of the basic necessities essential for survival of human beings, plants, trees, animals etc.
Therefore, it is important to save water by purifying or treating impure water so that it becomes suitable for use. Also, we can re-use waste water for different purposes except drinking.
Thus, we can conclude that the best method to conserve water is treating and re-using wastewater.