The correct option is C Cnidaria
Corals belong to the phylum Cnidaria. The great barrier reef, which is visible from space, is a colony of corals.
Phylum Protozoa comes under the kingdom Protista. It comprises unicellular microscopic organisms such as Amoeba and Paramecium.
Phylum Porifera includes the sponges.
Phylum Ctenophora consists of light emitting organisms such as Pleurobrachia.