Answer C refers to differential survival of moths with darker wings, and is correct. Answer A refers to all of the moths gradually becoming darker, this is inaccurate. Answer B refers to moths changing in response to a need to hide from birds. Although the peppered moth story is a classic example of natural selection and is found in many textbooks, the story is not as simple as it has been told. Birds hunting for moths may not really pick them out depending on whether or not they blend in with the trees. Recent research suggests that the melanic (dark) moths may have some survival advantage related to their metabolism in highly polluted areas.
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