What is the classification of arthropods recognized by their hard exoskeleton and segmented body?

The correct classification of arthropods is associated with their defining characteristics, which include a hard exoskeleton and a segmented body. This group, known as Arthropoda, encompasses a vast array of species, including insects, spiders, and crustaceans. The hard exoskeleton, made primarily of chitin, provides protection and structural support, allowing these organisms to thrive in various environments. The segmented body structure is another key feature, allowing for specialized functions within different body regions, such as the head, thorax, and abdomen in insects. This segmentation also facilitates mobility and flexibility.

Other choices present different phyla that do not share these specific characteristics. For example, Mollusca includes animals like snails and octopuses, which have softer bodies and often a calcium carbonate shell rather than a hard exoskeleton. Annelida, which encompasses segmented worms, has a different body plan and lacks an exoskeleton, relying instead on a moist body covering. Cnidaria includes jellyfish and corals, which have a polyp or medusa form and possess stinging cells, but do not have a hard exoskeleton or segmented bodies. Thus, only Arthropoda correctly fits the description of having a hard exoskeleton