Which of the following is an example of non-point source pollution?

Runoff from agricultural fields or urban areas is an example of non-point source pollution because it comes from multiple, diffuse sources rather than a single identifiable point. Non-point source pollution is often caused by rainfall or snowmelt moving over and through the ground, picking up pollutants such as fertilizers, pesticides, sediment, and other contaminants. This type of pollution is challenging to control and regulate because it does not have a specific discharge point; instead, it can enter water bodies from various locations across a landscape, leading to widespread environmental impacts.

In contrast, the other options represent point source pollution, where contaminants are released from a single, identifiable source. Discharge from a sewage treatment plant, water released from a factory, and a spill from a tanker all originate from specific locations and can be tracked back to their source, making them easier to manage and regulate compared to non-point sources.