Answer: The mantle.
- A The radula
- B The muscular foot
- C The gill filaments
- D The mantle
Correct answer: D. The mantle
Explanation: The mantle is a soft fold of the body wall that secretes the calcareous shell of molluscs.
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.