The answer is letter B.
Cnidaria is a phylum that contains over 10,000 of species of animals that are found exclusively in aquatic environments. These are predominantly marine species that have specialized cells called cnidocytes that are mainly used for catching prey. The structure of their bodies are made up of mesoglea, a non-living jelly-like substance and are radially symmetrical with their mouths surrounded by tentacles that carry the cnidocytes that sting and trap their prey enabling them to feed and survive.