Concept:The tadpole uses a structural feature for movement in water.Explanation:A tadpole swims by the side-to-side movement of its tail.Its gills are used for breathing underwater, not for swimming.A swim bladder is found in bony fish for buoyancy, not in tadpoles.Fins are not the main swimming organ of a tadpole.Thus, the tail is the adaptation that enables swimming in an aquatic habitat.Answer:C. Tail