Concept:The diagram shows eutrophication, which is the excessive growth of algae in water due to nutrient enrichment.Explanation:Nitrates and phosphates, such as NO3− and PO43−, are nutrients that encourage algal bloom.These nutrients enter water bodies from agricultural fertilisers and from sewage.Sewage contains organic waste and additional nutrients that also trigger rapid algal growth.Therefore, dumping sewage into water bodies can produce the same phenomenon shown in the diagram.Answer:C. dumping of sewage
