Answer:
Sickle-cell anemia is a genetic disorder that is caused by having two recessive alleles for the disorder. This means that an individual who has two copies of the recessive allele will develop the disorder, while an individual who has one copy of the recessive allele and one copy of the healthy allele will be a carrier for the disorder, but will not develop it.
Scientists have discovered that some people who are carriers of one allele for sickle-cell anemia are protected against malaria. This means that having one copy of the recessive allele confers some protective benefit against malaria, without causing sickle-cell anemia. Therefore, the genotype that would be the most advantageous to protect people against malaria without causing sickle-cell anemia is one that contains one copy of the recessive allele for sickle-cell anemia, and one copy of the healthy allele. This genotype would allow the individual to be protected against malaria, without developing sickle-cell anemia.