Identify major sources of chemical contaminants found in drinking water.

The choice of agricultural runoff, industrial discharges, and sewage effluents as major sources of chemical contaminants found in drinking water is accurate because these sources are well-documented contributors to water pollution.

Agricultural runoff often contains pesticides, herbicides, and fertilizers that can leach into nearby water bodies during rain events. These chemicals can create significant contamination issues, affecting both surface and groundwater sources used for drinking.

Industrial discharges refer to the release of pollutants from factories and manufacturing facilities. Many industries use and produce a variety of chemicals, including metals and solvents, that can contaminate nearby water sources if not properly managed.

Sewage effluents arise from wastewater treatment plants and can introduce pathogens and nutrients like nitrogen and phosphorus into water systems, posing health risks and contributing to problems such as algal blooms.

These three sources—agricultural, industrial, and sewage—are critical areas of concern for public health and environmental safety in relation to the quality of drinking water supplies. They are extensively studied in water quality management because of their significant impact on the presence of chemical contaminants.