What substance is added to the canteen for disinfection using calcium hypochlorite?

The correct choice involves calcium hypochlorite solution, which is used as a disinfectant for water purification. Calcium hypochlorite is a powerful oxidizing agent and serves as a chlorine source for disinfecting water by killing pathogens, including bacteria and viruses. When added to a canteen, it effectively sanitizes the water, making it safe for drinking.

Using calcium hypochlorite in a solution is a common practice in field sanitation to ensure that the water supply is safe for consumption during military operations or in emergency situations. This method is preferred because it is effective, provides residual disinfection, and is relatively easy to handle.

The other choices represent alternative substances that do not directly serve the same purpose in the context of disinfection using calcium hypochlorite. For instance, salt may be employed in various applications but lacks the disinfectant properties that calcium hypochlorite provides when added to drinking water. Similarly, bleach, while it contains chlorine, is not the same as calcium hypochlorite solution and is typically not used directly for water purification in field settings. Water purification tablets may also be effective but often consist of different chemical compounds and are a different method of ensuring water safety compared to the direct use of calcium hypochlorite