Abalone belongs to the monocoque mollusks; squid belongs to the mollusc class, is a kind of squid, body conical, body color pale, with light brown spots, head large, anterior born with 10 tentacles, tail end of the fleshy fins in a triangular shape, often swim in groups in the ocean at a depth of about 20 meters; seals live in the water, with the characteristics of the fetus lactation, belongs to the mammal; seahorses live in the water, gills to breathe, fins to swim, belongs to the fish. Fish. D can be seen in line with the meaning of the question. Therefore: D