Question

a well - known example of a balanced polymorphism is
○ acclimatization response.
○ body shape in cold climates.
○ red hair color.
○ sickle - cell anemia.

Explanation:

Balanced polymorphism occurs when two or more alleles are maintained in a population due to natural selection. Sickle - cell anemia is a well - known example. Heterozygous individuals for the sickle - cell allele have an advantage in malaria - endemic regions as they are more resistant to malaria compared to homozygous normal individuals, while homozygous sickle - cell individuals have the disease. This keeps both the normal and sickle - cell alleles in the population.

Answer:

sickle - cell anemia.