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A prokaryote is a unicellular organism that lacks a membrane-bound nucleus (karyon<span>), mitochondria, or any other membrane-bound organelle.</span>
Answer:
I'm presuming you mean the three different subcatagories or taxa as there around 25/26 mammalian orders. The three taxa are - Prototheria or Monotreme = Mammals that lay eggs Metatheria Marsupial = Mammals with external development pouches.
Explanation:
I think you are correct :) D