What are some common sources of water contamination?

The correct choice highlights key sources of water contamination that pose significant risks to both human health and the environment. Agricultural runoff often contains fertilizers, pesticides, and herbicides that can leach into water bodies, leading to nutrient pollution and degradation of aquatic ecosystems. Industrial discharge may introduce heavy metals, chemicals, and other pollutants directly into water sources, which can have harmful effects on wildlife and human health. Wastewater treatment plants, while essential for processing sewage and wastewater, can still release contaminants, especially if they are not adequately treated, leading to water quality issues in receiving waters.

The other options, while they represent various water sources, do not directly outline common causes of contamination. Rainwater and mountain streams are typically considered natural sources of relatively clean water, although they can be contaminated under certain conditions, such as through urban runoff. Ocean water and freshwater lakes are ecosystems that can also be affected by pollution, but they are not direct sources of contamination themselves. Natural mineral deposits can contribute to water quality issues, such as hardness or specific contaminants, but they are not typically classified as common sources of water contamination in the same manner as agricultural, industrial, and wastewater influences.