1. When an acid is dissolved in water, the process is highly exothermic, meaning that it releases a significant amount of heat.2. If the acid is added to the water, it can cause the water to heat up rapidly and potentially boil or splatter, which can be dangerous.3. In addition, adding water to acid instead of acid to water helps to ensure that the acid is more evenly distributed in the solution, which can help to prevent localized overheating.4. Therefore, it is advised that while diluting an acid, one should add water to acid and not acid to water, and continuously stir the solution to ensure even mixing.5. Therefore, Both the assertion and the reason are correct and R is the correct explanation of A.