The correct answer is option B. animal was endothermic and had a high metabolic rate.
In a closed circulatory system, the blood is constantly constrained within vessels of various sizes. The heart pumps blood in this circulation, which causes mammals' metabolic rates to be high. Aves and mammals are endothermic (body temperature-regulated) creatures. Warm blooded people.
When a four-chamber heart is present, the circulation is stopped. As a fossil animal resembles aves, the alternative is to use it. Animal was endothermic, had a high metabolic rate, and a closed circulatory system.
Mammal's closest relative All endothermic animals, including birds and mammals, have fully separated ventricles and a four-chambered heart, whereas amphibians have a three-chambered heart and the majority of reptiles, with the exception of the crocodile, have a three-chambered heart. Fishes are known to have hearts with two chambers.
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