An anthropologist discovers the fossilized heart of an extinct animal. The evidence indicates that the organism's heart was large, well-formed, and had four chambers, with no connection between the right and left sides. A reasonable conclusion supported by these observations is that the animal wasA) most closely related to mammals. B) most closely related to fish. C) most closely related to reptiles. D) most closely realted to athropods and molluscs. E) most closely related to amphibians.

Option A, most closely related to mammals

Explanation:

Insects like arthropods and molluscs have an open circulatory system and thus do have a distinguishable heart. Fish has two chambered heart. Reptiles have three chambered heart. Amphibians too have a three chambered heart.  

All mammals and fish have four chambered heart. The right and left sides of the chambers have restricted entry and hence remain intact from each other

Hence, option A is correct

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