The correct option is D They have stronger muscles in their foot.
∙ Fishes have fins that helps them to keep the balance of the body. It also helps them to keep direction while swimming. Fins of the tail help the fish to swim ahead.
∙ Fishes have a streamlined body. This allows the fish to easily move in water.
∙ The skeleton of the fish is covered with strong muscles which helps them in swimming. These muscles mostly make up the front part of the body to curve to one side, while the tail part swings the opposite side.
∙ Stronger muscles in foot is seen in snails.