Answer: D. A river separates members of a squirrel population that used to occupy the same geographical area.
Explanation:
Allopathic Speciation occurs when a geographic barrier (river, mountain, or canyon) separates members of a population
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It depends on which virus you are referring to specifically. Viruses come in many shapes and types; their variations are tremendous.
For HIV and Influenza, viruses acquire their envelops after maturation, during the budding off or detachment stage from the host cell.
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