Answer: C) phosphate and nitrogen pollution
Explanation:
Eutrophication is a phenomena in which the water body which consists of high concentration of fertilizers drained in a water body by agricultural field runoff. The fertilizers typically composed of phosphates and nitrogen results in growth of aquatic plants and extensive algal growth on the surface of water. This leads to the depletion of oxygen levels in the water body. As a result of this the water exhibit a foul smell and the aquatic animals decline in numbers.
According to the given situation, the large amount of algae in a lake is because of the increase in the phosphate and nitrogen pollution. The increase in concentration of the phosphate and nitrogen will lead to the phenomena of eutrophication.
