Correct Answer: Untreated sewage

Solution : The correct answer is (C) Untreated sewage

In urban areas, the major cause of water pollution is often the discharge of untreated sewage into water bodies. Urban centers generate significant amounts of wastewater containing various pollutants, including human waste, chemicals, and microorganisms. When untreated sewage is directly discharged into rivers, lakes, or oceans, it can contaminate the water and pose risks to both human health and aquatic ecosystems.