You are presented with the question "What forms in shallow tropical water?" and the following answer choices: 
- blobfish
 - sub-units of species
 - accumulated exoskeletons
 - aqueous solution
 - polar bears
 - an area swollen with pus
 - swamp vegetation
 - deep-sea dwellers

Now knowing that corals form large colonies in shallow tropical water and coral reefs are made up of the accumulated exoskeletons of the coral polyp, choose the best answer.


 

   accumulated exoskeletons      