An arthropod and a nematode are grouped together in modern discussions because both shed an outer cuticle during growth. In an exam answer, the key reason is: (229)

Molting or ecdysis is a key ecdysozoan character. Arthropods molt a chitinous exoskeleton, and nematodes molt a cuticle during growth. This question is designed as a comparison-based item to reduce thin-content style repetition and improve conceptual depth.