Answer: The correct answer is- Starfish.
Radial symmetry depicts a body plan of an organism, which can be divided into two equal halves when a plane from any angle passes through central axis of the body.
Starfish is radially symmetrical organism as any plane can divide its body into two equal halves.
On the contrary, flatworm, butterfly, and tadpole show bilateral symmetry ( only single axis/ plane can divide the body into two equal halves.