Answer: Cnidarians.
- A Cnidarians
- B the roundworms group
- C only the molluscs
- D a set of sponges
Correct answer: A. Cnidarians
Explanation: Cnidarians bear nematocysts on their tentacles.
Moving across the animal phyla, body organisation becomes progressively more complex: from no symmetry and cellular organisation (Porifera) through radial/diploblastic (Cnidaria), bilateral/acoelomate (Platyhelminthes), pseudocoelomate (Nematoda), to a true coelom with full organ systems (Annelida and beyond).
Concept context
Phylum-level classification of the animal kingdom from Porifera to Chordata, based on body symmetry, coelom, and segmentation. One of the most example-heavy chapters for NEET.