What did you learn about Evolution and how Darwin made these discoveries.

The Origin of Species

By that time, having studied multiple texts and having done multiple scientific studies on his own, Darwin had developed what would become known as his theory of evolution. In 1859, Darwin's most famous work, Origin of Species by Means of Natural Selection, was published.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."