You are presented with the question "What constructs an exoskeleton using calcium carbonate?" and the following answer choices: 
- animals
 - amoeba
 - sharks
 - insects
 - mammals
 - Man
 - coral
 - bats

Now knowing that many corals secrete an exoskeleton that builds up to become a coral reef and hard corals build by secreting calcium carbonate skeletons, choose the best answer.


 

       coral  