How does the coral animal build a stony reef?

Coral reefs are built by coral polyps as they secrete layers of calcium carbonate beneath their bodies. The corals that build reefs are known as “hard” or “reef-building” corals. ... The coral polyps that build the reef survive by forming a symbiotic relationship with microscopic algae called zooxanthellae.

dz nuts.   eeneneneeenenne

answer:

sequence 1- deletion

                  2- duplication

                  3- insertion

                  4- substitute

                  5- inversion