An animal has a triploblastic body, bilateral symmetry, a pseudocoelom, and a complete digestive system but lacks circulatory and respiratory systems. Which phylum does it most likely belong to?

Correct answer: B. Nematoda

Explanation: Nematodes are triploblastic, bilaterally symmetrical, pseudocoelomate animals with a complete alimentary canal but no circulatory or respiratory system, exemplified by Ascaris and Wuchereria.