Eutrophication is the natural aging of a lake by nutrient enrichment of its water. With time, streams draining into the lake introduce nutrients such as nitrogen and phosphorus and domestic sewage, which encourage the growth of aquatic organisms.
As the lakes fertility increases, algal bloom occurs. Algal bloom causes the degradation of water quality and fish mortility and dead remains begin to be deposited on the lake bottom. Over the year, lake finally converted into the land. Thus, the correct answer is option D.