Which Statement Is NOT True About the Maintenance of Variation

Which statement is NOT true about the maintenance of variation in a population?

A) Selection for adaptation to a particular environment ensures that the population will become stronger and more viable under any and all conditions.
B) Only phenotypes are acted on by selection,so heterozygotes serve as a reservoir of recessive alleles that may be adaptive in a different environment.
C) Heterozygote superiority may lead to selection for the heterozygote above either homozygote.
D) Variation is maintained through mutation,recombination,gene flow,and changed conditions.
E) Variations allow for the presence of conditions such as sickle-cell anemia.