You are presented with the quiz "many corals secrete an exoskeleton that builds up to become what?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "many corals secrete an exoskeleton that builds up to become a coral reef" and "coral Reefs Coral reefs are the jungles of the sea". 

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


 

  jungles of the sea         