If many corals secrete an exoskeleton that builds up to become the jungles of the sea, then many corals secrete an exoskeleton that builds up to become what?

Answer choices:
- important habitats
 - jungles of the sea
 - seaweed
 - gastropod shells
 - food and shelter
 - dolphins
 - major threat to health
 - oceans

 

  jungles of the sea        