Final answer:
Fertilizer spread over a farmer's field is an example of nonpoint source pollution, which is diffuse and difficult to connect to a single source, unlike point source pollution that comes from identifiable locations. The correct option is option c.
Step-by-step explanation:
An example of nonpoint source of water pollution is fertilizer spread over a farmer's field. Nonpoint source pollution refers to the contamination that occurs when small amounts of pollutants collect in a large area, such as agricultural fields, urban areas, and abandoned mines.
One of the main challenges with such pollution is that it is diffuse, making it difficult to pinpoint a single origin for the contaminants. In contrast, point source pollution can be traced back to a specific, identifiable source, such as a pipe from a sewage treatment plant or factory.