Option 1 states that both the Assertion (A) and the Reason (R) are true, and R is the correct explanation of A.

The Assertion states that water in an open pond remains cool even on a hot summer day. This is because water has a high specific heat capacity, meaning it can absorb and retain a large amount of heat energy without a significant change in temperature. As a result, when the surrounding air is hot, the water in the pond absorbs some of the heat from the air but does not increase in temperature significantly, keeping the water cool.

The Reason states that on heating, water evaporates and the heat energy is converted into latent heat. This is true because when water is heated, its molecules gain energy and move faster, leading to an increase in temperature. When the temperature reaches the boiling point, the water molecules gain enough energy to overcome the intermolecular forces and escape from the liquid phase as vapor. This process of evaporating water requires a significant amount of heat energy, called latent heat. The conversion of heat energy into latent heat during evaporation helps cool the remaining water in the pond.

Therefore, both the Assertion and Reason are true, and the Reason correctly explains why the Assertion is true.