You are presented with the quiz "Which species doesn't have an anterior or posterior end?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "adult echinoderms have radial symmetry" and "animals with radial symmetry lack an anterior and posterior end". So, what's the best answer to the question?

Options:
*animals;
*peachleaf willow;
*Rabbits;
*Blowfish;
*fur seals;
*Snakes;
*Echinoderms;
*alpacas;
The answer is:
Echinoderms