Which method is effective for purifying water?

Boiling water is an effective method for purifying it, primarily because the high temperature kills many types of pathogens, including bacteria, viruses, and parasites that can cause illness. Heating the water to a rolling boil for a few minutes is usually sufficient to ensure that the majority of these harmful microorganisms are eliminated. This method is widely recommended by health organizations, especially in situations where water quality is uncertain.

Other methods listed, such as filtering through sand, can remove larger particles and some sediment but may not effectively eliminate all pathogens present in the water. Stirring with a spoon does not purify water in any way, as it simply moves the water around without addressing contaminants. Adding sugar does not purify water either; instead, it introduces a substance that could potentially contaminate the water further. Therefore, boiling is the most reliable and widely accepted method for purifying water in many emergency scenarios or when safe drinking water is not available.