Choose the correct statement. All Pisces have gills covered by an operculum. All reptiles have a three-chambered heart. All mammals are viviparous. All cyclostomes do not possess jaws and paired fins.

All reptiles have three-chambered heart except crocodiles, they have four-chambered heart. Class Chondrichthyes are cartilaginous fishes that lack operculum. Monotremes are egg-laying mammals. Agnatha/ Cyclostomata is the historical class of jawless fishes that lack paired fins without any exception. Therefore, the correct answer is option D.