Question

Which of the following animal species includes segmented worms?
A. Annelida
B. Arthropoda
C. Mollusca
D. None of the above

Answer 1

Hint: The features like elongated, more or less cylindrical bodies divided by grooves into a series of ring-like segments gave the name segmented worms to these worms. They divide the internal body space into a series of compartments. It is because their grooves correspond to interior partitions called septa.

Complete answer: An arthropod is a species that includes all invertebrates (lacking the vertebral column). Animals in this kingdom have an exoskeleton (external skeleton), a segmented body, and jointed appendages. Arthropoda is triploblastic and has a true coelom. The animals possess bilateral symmetry. Its body is divided into three parts. These three parts are -head, thorax, and abdomen. Arthropoda has segmentation as a character. The phylum does not include worms.
Phylum Annelida, the Annelids are found in aquatic as well as terrestrial environments. These are bilaterally symmetrical invertebrate organisms. They have a segmented body that is a distinguishable feature, from any other organism. The Annelids are coelomate and triploblastic. They exhibit organ level organization. Their body is segmented. They respire through their body surface. Annelids are the phylum of the segmented worms.
In phylum Mollusca, animals have soft-bodies, triploblastic, and bilaterally symmetrical, and coelomate. They are mostly found in marine and freshwater. They exhibit an organ system level of organization. The body of the Molluscs is divided into head, visceral mass, muscular foot, and mantle. The head comprises tentacles and compound eyes.
A calcareous shell covers the body. Molluscs do not have segmentation in their bodies.
Hence, the correct answer is option A.

Note:
Phylum Annelida has the characteristic feature of having segmented worms. Annelids are also known as ringed worms. They exhibit organ level organization. They have a segmented body that is a distinguishable feature. Earthworm and leeches are two common examples of having a segmented body.