Which of the following explains why genetic variation is necessary for evolution to occur in a population?

Question

anonymous · Answer

A.	Without genetic variation, alleles in populations would cross over twice, so that the DNA would remain the same in a population, and evolution would not occur.
	B.	Without genetic variation, asexually-reproducing organisms could not mate and their species would die out.
	C.	Without genetic variation, DNA would stay the same from generation to generation, preventing the processes of evolution.
	D.	Without genetic variation, mutations would occur, wiping out entire populations before they could evolve.