Explanation

Water has a very large latent heat of vaporisation (about 2260 kJ/kg), so when sprinkled on a hot rooftop it evaporates by absorbing a large amount of heat from the roof surface. This evaporative cooling lowers the roof's temperature after a hot sunny day. Option (B) is wrong on facts too: water actually has a high specific heat capacity, not a lower one. Availability of water (C) is incidental, not the physical cause. The cooling effect is therefore due to the large latent heat of vaporisation, option (D).