Eutrophication of a lake is most directly caused by:
Correct: B
Eutrophication is the process by which a body of water becomes enriched with excessive nutrients, particularly nitrogen and phosphorus, often from agricultural runoff, sewage discharge, or fertilizer leaching. These nutrients stimulate excessive growth of algae and aquatic plants (algal blooms). When these organisms die, their decomposition by aerobic bacteria consumes dissolved oxygen, leading to hypoxic or anoxic conditions that kill fish and other aquatic organisms. This process is called cultural or anthropogenic eutrophication.