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THE CORRECT ANSWER: It is a lung-breathing, warm-blooded marine mammal.

Cetaceans are an order of aquatic mammals that include whales, dolphins and porpoises. Unlike fish, they do not have gills and must come to the surface to breathe air through their blowhole.Their physiology is remarkable: they are homeothermic, that is to say they maintain a constant body temperature thanks to a thick layer of insulating fat called bacon. They also breastfeed their young with extremely high-fat milk to promote rapid growth.They are divided into two groups: the odontocetes, which have teeth (like the orca or the bottlenose dolphin), and the mysticetes, which have baleen to filter plankton (like the humpback whale). Their adaptation to the marine environment is so perfect that they spend their entire life cycle in water, developing sophisticated echolocation abilities to communicate and hunt in the darkness of the ocean depths.