Correct Answer: A
Explanation:
Darwin did not know of mutations, so choice (A) is the correct answer. Fundamental to his idea of natural selection was that, in order, (1) organisms produce more offspring than can survive and, (2) due to competition, not all organisms will survive, which means, (3) some organisms will be more fit to survive than others, and (4) variation may be the reason for the difference in survivability.