Which of the following is a true statement concerning genetic variation?

A)It is created by the direct action of natural selection.
B)It arises in response to changes in the environment.
C)It must be present in a population before natural selection can act upon the population.
D)It tends to be reduced by the processes involved when diploid organisms produce gametes.
E)A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity.