Most poisonous pollutant in water is

Answer: Option C

Most poisonous pollutant in water is Phosphate.
Water pollutants include contamination due to domestic wastes, insecticides and herbicides, food processing waste, pollutants from livestock operations, volatile organic compounds, heavy metals, chemical waste and others.
Phosphorus is an essential element for plant life, but when there is too much of it in water, it can speed up eutrophication of rivers and lakes.