Correct Option: D

Eutrophication is the natural ageing of a lake due to excessive entry of nutrients into water. The streams draining into the lake introduce nutrients such as nitrogen and phosphorus that encourages the growth of algae at the surface of water or pond. The excessive acummulation of algae at the surface of pond is called algae bloom, Later due to death of these algae, their organic matter get decomposed due to which oxygen gets depleted and thereby aquatic animals die. If these activities keeps on occuring for a long time, then the pond may have more organic matter and less water.