Concept:The presence of
Vibrio cholerae, a disease-causing bacterium, in public drinking water shows that the water is contaminated and not safe for drinking.
Explanation:Vibrio cholerae is the bacterium that causes cholera.
Finding it in public drinking water means the water has been polluted with sewage or human waste.
Polluted water carries harmful germs and is unfit for human use.
Therefore, its detection is a direct sign of water pollution, not of clean water or decayed organisms alone.
While it could lead to a disease outbreak, the presence of the bacterium itself is evidence of contamination.
Answer:C. water pollution.