A flatworm and a roundworm are placed side by side. The roundworm is recognized by a cylindrical body, complete gut, and pseudocoelom. In an exam answer, the key reason is: (277)

Correct Answer: B

cylindrical body with pseudocoelom and complete gut

Nematodes are cylindrical pseudocoelomates with a complete digestive tract. Flatworms are flattened acoelomates and usually have an incomplete gut or no gut in tapeworms. This question is designed as a comparison-based item to reduce thin-content style repetition and improve conceptual depth.