Answer:
B. The increase is due to industrial point source pollution.
Step-by-step explanation:
Pollution is the release of harmful substances into land, air or water. The harmful or toxic substances are called POLLUTANTS. According to this question, a community discovers via analysis that its river is now polluted with small amounts of over 20 different chemicals.
This chemicals is a pollutant that can likely emanate from industrial companies and industries that produces these harmful chemicals as waste. Hence, the increase is due to industrial point source pollution.