Q: Corals build hard exoskeletons that grow to become coral what?


Read this paragraph and choose the correct option from the provided answers:

Cnidarians are aquatic invertebrates in Phylum Cnidaria. They include jellyfish and corals, both of which have radial symmetry. All cnidarians have nematocysts, and many are bioluminescent. They may exist in medusa and/or polyp form. Corals build hard exoskeletons that grow to become coral reefs.

 Choices:

- beds

- layers

- crystals

- reefs


A:
reefs