For semester exam preparation, consider this situation: aquatic molluscs exchange gases through comb-like structures in the mantle cavity. The correct conclusion is:

Correct Answer: D

gills called ctenidia

Molluscan gills are called ctenidia. They are usually located in the mantle cavity and may also assist in feeding in bivalves. This MCQ belongs to the Mollusca topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.