Final answer:
Reef-producing corals are called b) hermatypic. Coral reefs are formed by the calcium carbonate skeletons of coral organisms that have a mutualistic relationship with photosynthetic unicellular algae called zooxanthellae, allowing large corals to grow and contribute to the formation of coral reefs.
Step-by-step explanation:
Reef-producing corals are called hermatypic.
Coral reefs are formed by the calcium carbonate skeletons of coral organisms, which are marine invertebrates in the phylum Cnidaria. These corals have a mutualistic relationship with photosynthetic unicellular algae called zooxanthellae.
The corals provide a protective environment and nutrients for the zooxanthellae, and in return, the zooxanthellae provide the corals with the majority of the nutrition and energy they require.
This mutualistic relationship allows large corals to grow and contribute to the formation of coral reefs.