Information:  - In zoological nomenclature, a subphylum is a taxonomic rank below the rank of phylum.   - In biology, a phylum (plural: phyla) is a taxonomic rank below kingdom and above class. Traditionally, in botany the term division was used instead of "phylum", although from 1993 the International Code of Nomenclature for algae, fungi, and plants accepted the designation "phylum". Depending on definitions, the kingdom Animalia contains approximately 35 phyla, Plantae contains about 12, and Fungi contains around 7. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta.  - Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or "basket stars". About 1,500 species of starfish occur on the seabed in all the world's oceans, from the tropics to frigid polar waters. They are found from the intertidal zone down to abyssal depths, below the surface.  - Tube feet are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers. They are part of the water vascular system.  - The term sand dollar (or sea cookie or snapper biscuit in New Zealand, or pansy shell in South Africa) refers to species of extremely flattened, burrowing sea urchins belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are known as sea biscuits. Related animals include other sea urchins, sea cucumbers, and starfish.  - Echinoderm is the common name given to any member of the phylum Echinodermata (from Ancient Greek, , "echinos"  "hedgehog" and , "derma"  "skin") of marine animals. The adults are recognizable by their (usually five-point) radial symmetry, and include such well-known animals as sea stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest grouping of deuterostomes (a superphylum), after the chordates (which include the vertebrates, such as birds, fishes, mammals, and reptiles). Echinoderms are also the largest phylum that has no freshwater or terrestrial (land-based) representatives.  - Eleutherozoa is a subphylum of echinoderms . They are mobile animals with the mouth directed towards the substrate . They usually have a madreporite , tube feet , and moveable spines of some sort , and some have Tiedemann 's bodies on the ring canal . All living echinoderms except Crinoidea belong here .  - The madreporite is a lightcolored calcareous opening used to filter water into the water vascular system of echinoderms. It acts like a pressure-equalizing valve. It is visible as a small red or yellow button-like structure, looking like a small wart, on the aboral surface of the central disk of a sea star. Close up, it is visibly structured, resembling a "madrepore" (stone coral, Scleractinia) colony. From this, it derives its name.  - Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that live on the seabed and build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc with a mouth and a fringe of tentacles. Although some species are solitary, most are colonial. The founding polyp settles on the seabed and starts to secrete calcium carbonate to protect its soft body. Solitary corals can be as much as across but in colonial species the polyps are usually only a few millimetres in diameter. These polyps reproduce by budding but remain attached to each other, forming a multi-polyp colony with a common skeleton, which may be up to several metres in diameter or height according to species.  - Sea urchins or urchins, archaically called sea hedgehogs, are small, spiny, globular animals that, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. About 950 species of echinoids inhabit all oceans from the intertidal to deep. The shell, or "test", of sea urchins is round and spiny, typically from across. Common colors include black and dull shades of green, olive, brown, purple, blue, and red. Sea urchins move slowly, feeding primarily on algae. Sea otters, starfish, wolf eels, triggerfish, and other predators hunt and feed on sea urchins. Their roe is a delicacy in many cuisines. The name "urchin" is an old word for hedgehog, which sea urchins resemble.    After reading the paragraphs above, choose the best answer for the entity that related to 'eleutherozoa' with the relationship of 'parent taxon'.  Choices: - cnidaria  - echinodermata  - fungi  - hedgehog  - madrepore  - phyla  - sand dollar  - scleractinia  - starfish  - triggerfish
A:
echinodermata