Editorial: Almost every year the Smithfield River floods the coastal fishing community of Redhook, which annually spends $3 million on the cleanup. Some residents have proposed damming the river, which would cost $5 million but would prevent the flooding. However, their position is misguided. A dam would prevent nutrients in the river from flowing into the ocean. Fish that now feed on those nutrients would start feeding elsewhere. The loss of these fish would cost Redhook $10 million annually. Which one of the following most accurately expresses the main conclusion of the editorial's argument? ['The Smithfield River should be dammed to prevent flooding.', 'Nutrients from the Smithfield River are essential to the local fish population.', 'For Redhook to build a dam on the Smithfield River would be a mistake.', 'The Smithfield River floods cost Redhook $3 million every year.']