After a hot sunny day, people sprinkle water on roof top because the large latent heat of vaporisation of water helps to _____surface.

People sprinkle water on the roof or open ground on a hot sunny day to cool down the surrounding environment. The process of sprinkling water on a hot surface causes the water to evaporate, which helps to absorb the heat from the surrounding area. This is because the energy required to convert water from a liquid to a gas state is taken from the surrounding environment, resulting in a cooling effect.

When water is sprinkled on a roof or open ground, it cools down the surface temperature of the area, making it more comfortable to walk or stand on.

Hence option A is correct.