Answer:
The skeletons of coral polyps
Step-by-step explanation:
A coral is a colony of many individual animals called polyps, originating from the replication of an initial polyp. The coral reef is made up of “zillions” of coral colonies and other limestone-depositing organisms, growing amidst the skeletons of their predecessors and the sand and sediment derived from them. Most of the dissolved carbon in the ocean is used to form the skeletons of coral polyps.