Which of the following is a monophyletic group?

Question

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Mammals are a monophyletic group because they include a common ancestor and all of its descendants that possess hair, mammary glands, and a unique middle ear bone structure. The other groups listed (fishes, dinosaurs excluding birds, and amphibians) are paraphyletic or polyphyletic because they do not include all descendants of a common ancestor, as some members have been removed from the group. For example, birds are descended from dinosaurs, so excluding birds from dinosaurs makes the group paraphyletic.

Which of the Following Is a Monophyletic Group