The correct answer is C. Arthropods.
Arthropods are the most diverse phylum of animals, with over 1.5 million known species. They are characterized by their segmented bodies, jointed appendages, and exoskeletons made of chitin. The body of an arthropod is typically divided into three regions: the head, thorax, and abdomen. The head contains the mouthparts, eyes, and antennae. The thorax bears the legs and wings, if present. The abdomen contains the digestive, reproductive, and excretory organs.
Annelids are a phylum of segmented worms that includes earthworms, leeches, and marine worms. They have a long, cylindrical body that is divided into many segments. Each segment has its own set of organs, including a digestive system, a nervous system, and a reproductive system. Annelids are bilaterally symmetrical, meaning that they have a left and right side that are mirror images of each other.
Chordates are a phylum of animals that includes vertebrates, as well as some invertebrates such as tunicates and lancelets. Chordates are characterized by a notochord, a rod-shaped structure that runs along the back of the animal. The notochord provides support and helps the animal to move. Chordates also have a dorsal hollow nerve cord, a series of gill slits, and a post-anal tail.
Echinoderms are a phylum of animals that includes sea stars, sea urchins, sand dollars, and sea cucumbers. Echinoderms are characterized by their radial symmetry, their spiny skin, and their water vascular system. The water vascular system is a network of canals that runs through the body of the animal. It is used for locomotion, feeding, and respiration.
In conclusion, the correct answer is C. Arthropods. The body of an arthropod is typically divided into three regions: the head, thorax, and abdomen.