You are presented with the question "what do coral polyps form?" and the following answer choices: 
- lagoon
 - graptolites
 - a cuticle
 - barnacles
 - bioaerosols
 - cave
 - coral reef
 - salt and water.

Now knowing that many corals secrete an exoskeleton that builds up to become a coral reef and coral reefs are made up of the accumulated exoskeletons of the coral polyp, choose the best answer.


 

       coral reef  