ANS:A - large latent heat

Only a small amount of evaporation of water produces large cooling effects because of its large latent heat. Latent heat refers to the amount of heat absorbed or released during a phase change of a substance at constant temperature and pressure. Water has a relatively high latent heat of vaporization, which means that a large amount of energy is required to change water from liquid to vapor phase, or vice versa, at its boiling point. When water evaporates, it absorbs heat from its surroundings to provide the energy needed for the phase change. This results in a cooling effect in the surrounding environment, as the heat energy is transferred from the surroundings to the water molecules undergoing evaporation. Because water has a large latent heat of vaporization, even a small amount of water evaporation can absorb a significant amount of heat from its surroundings, leading to a noticeable cooling effect. This property makes water an effective coolant in various applications, such as sweating in mammals, evaporative cooling systems, and air conditioning units.