Which class belongs to Arthropoda?

• A. Insecta
• B. Mollusca
• C. Echinodermata
• D. Annelida

Answer: (A)

Understanding how animals are grouped helps here. Arthropoda is a phylum defined by an external skeleton, a segmented body, and jointed appendages. Insecta is a class within that phylum because insects have a three-part body (head, thorax, abdomen), six legs, and typically wings, all riding on a jointed exoskeleton. The other options aren’t members of Arthropoda at the class level—they belong to different phyla: Mollusca includes animals like snails and clams with a soft body and often a shell; Echinodermata includes sea stars and urchins with radial symmetry and a water vascular system; Annelida includes segmented worms with bristles called setae. So Insecta is the correct class that truly fits within Arthropoda.