I believe it is A as well
After hundreds or even thousands of generations both alleles for sickle cell anemia are still common in those of African ancestry. This is supported by two mechanisms: heterozygote advantage and gene flow.
Heterozygote advantage
When an allele is said to be heterozygous, it is carrying one copy of a gene. For example if one carries a copy of sickle cell allele, it will stay in the population even after many generations — natural selection will not be able to remove it and it will be passed on through generations. So, having one copy of that allele is advantageous but not deleterious.
Gene flow
With humans migrating throughout the different parts of the world, sickle cell allele is passed from one person to another or in different populations. It is actually advantageous to have one copy of this allele especially if there’s malaria in the area, which the allele is resistant.
Fun Facts
Wild Koala Day Exists
Koalas:
have fingerprints
don't have to drink (much) water
smell like eucalyptus
Are picky eaters
Have to Eat a LOT
have some extra junk in the trunk
Are loners
hug trees to keep cool
exhibit same gender mating behavior
90 percent of female koalas have chlamydia
females' stomach pouches, where their babies live for a few months after they're born
onetreeplanted
animalsmom
mentalfloss
Nitrogen Fixation is what it's called
Hope I helped
