Division of labor is not seen in which of these multicellular animals?

Explanation

Hydra and Euplectella do not show division of labor because they have a very simple body organization. Hydra has only tissue-level organization, so most of its cells perform more than one function instead of being specialized. Euplectella (a sponge) shows only cellular-level organization and lacks true tissues and organs, therefore division of labor is absent. In contrast, the blood fluke shows division of labor as it has an organ-system level of organization with specialized organs performing specific functions.So D is the correct option.