Which of the following is a possible source of phosphorus to a lake?

Phosphorus is a nutrient that can significantly impact aquatic ecosystems, leading to issues such as algal blooms when present in excess. Each of the listed sources can contribute phosphorus to a lake.

Wastewater discharge often contains phosphorus from human waste, detergents, and other household products. Treatment plants may not completely remove phosphorus, allowing it to enter nearby water bodies.

Industrial discharge can also be a source, as many industries use phosphorus in their processes or release phosphate-containing materials, contributing to nutrient loading in water systems.

Agricultural runoff is a significant contributor to phosphorus loading in lakes. Fertilizers applied to crops typically contain phosphorus, and during rain events, runoff can carry these nutrients directly into nearby lakes and streams, promoting eutrophication.

Since all of these sources can release phosphorus into aquatic systems, the most inclusive answer indicating that any of these can be a possible source is indeed correct.