Answer:
The correct answer here is C: difficult to trace because it comes from different sources.
Step-by-step explanation:
Nonpoint source pollution, also known as NPS, is defined as the pollution that collects on surface water sources and underground water sources due to rainfall, or snowfall, that covers landscapes that have been polluted by man, or nature itself, and whose run-off takes with it these pollutants into the water sources. Because of the nature of NPS, how diffused it is, it is not always possible to pinpoint the source of pollution and it is difficult also to revert.