Corals belong to which class of the Cnidaria— Anthozoa, Hydrozoa, Scyphozoa, or none of these?

The Phylum known as Cnidaria are organisms which are radially symmetrical. They have a mouth surrounded by tentacles which are used to capture prey.

One interesting fact about these organisms are their stinging cells, also known as nematocysts or cnidoblasts. These animals sting their prey, and the tentacles then push the food into the mouth.

The class known as Anthozoa include sea anemones and coral animals. They look like a flower. Their body is cylindrical with tentacles at the top surrounding their mouth. These organisms spend their time in the body form known as a polyp—these are sessile, which means they don't move about freely. Other types of Cnidaria like the jellyfish have a motile stage known as a medusa with a bell-shaped body and a mouth facing downward, surrounded by tentacles. Medusa can be seen freely moving at the surface of the ocean. These are in a different class called Scyphozoa.

Corals are colonial animals. They can produce a skeleton composed of calcium carbonate, which is limestone. As older corals die, new ones are built on top of the structure, which becomes a coral reef. The reef forms an important habitat that attracts many different arthropods, fish, mollusks, echinoderms and other organisms which are involved in shallow, warm-temperature ocean food webs.

To summarize, Anthozoa is the Class in the Phylum Cnidaria to which Coral animals belong.