You are presented with the quiz "Adult spiny skinned animals found only in marine environments have what?" 

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 "echinoderms are spiny skinned animals found only in marine environments". 

So, what's the best answer to the question?


 

        radial symmetry   