Final answer:
The most credible source for Scott's article about the potential contamination of the water supply by an industrial plant would be a scientist who specializes in the chemicals in question.
Step-by-step explanation:
When Scott is working on his piece for the local paper regarding an industrial plant that may have allowed toxic chemicals into the water supply, the most credible source for an interview would be c) A scientist at a local university who specializes in the chemicals in question. This person would likely have the most relevant expertise and factual information about the potential effects and risks associated with the chemicals, and could provide an informed perspective based on scientific knowledge and research.
Interviewing this scientist will contribute to a more accurate, expert understanding of water pollution issues and the impact of industrial chemicals on the environment and public health. Drawing insights from a scientific expert can also help readers understand the scope of pollution, its sources - such as point-source contamination - and the potential health effects as seen in toxicity studies.