The correct answer is A. flat water surface.
Evaporation is the process by which water changes from a liquid to a gas or vapor. It is a physical change, not a chemical change. Evaporation occurs when water molecules at the surface of a liquid have enough energy to escape the attraction of the other water molecules and enter the air as a gas.
The rate of evaporation depends on several factors, including the temperature of the water, the surface area of the water, and the wind speed. The higher the temperature of the water, the faster the water molecules will move and the more likely they are to escape into the air. The larger the surface area of the water, the more water molecules there are at the surface and the faster they will evaporate. The faster the wind speed, the more water molecules will be carried away from the surface of the water and the faster they will evaporate.
A flat water surface has the largest surface area and is therefore the most efficient at evaporating water. A convex water surface has a smaller surface area than a flat water surface and therefore evaporates water more slowly. A concave water surface has an even smaller surface area than a convex water surface and therefore evaporates water even more slowly.
Therefore, under the same conditions, a flat water surface will give the highest rate of evaporation.