Which organism is an annelid?

• A. Crab
• B. Nematode
• C. Earthworm
• D. Octopus

Answer: (C)

Annelids are segmented worms, built from repeating body units along their length. That segmentation, or metamerism, is a hallmark feature you can see in earthworms—their bodies have clear, ring-like segments and often tiny bristles called setae that help them move. This combination of true segmentation and a coelomates body plan places earthworms squarely in the phylum Annelida.

The other animals belong to different groups: crabs are crustaceans with an exoskeleton and jointed limbs (arthropods), nematodes are unsegmented roundworms with a pseudocoelom, and octopuses are mollusks (cephalopods) with soft bodies and no segmented structure.