Though Sickle-Cell Anaemia Is Frequently Lethal for Individuals Who Are

Multiple Choice

Though sickle-cell anaemia is frequently lethal for individuals who are homozygous for the sickle-cell allele,natural selection seems to have maintained that allele in certain geographic locations.A likely explanation for this observation is that

A) the forward mutation rate to sickle-cell is much higher in those regions.
B) individuals with sickle-cell anaemia live longer and have more children.
C) reversion from sickle-cell to wild-type is prevented in some populations.
D) individuals who are heterozygous for the sickle-cell allele are protected from malaria.
E) only certain populations have been tested for the presence of the sickle-cell allele.