Answer:
The correct answer would be AA and aa.
Natural selection is a natural phenomenon by which organisms with survival or advantageous traits tend to survive and reproduce more as compared to the organisms which lack those traits.
Consequently, the frequency of the advantageous traits increases in a population.
In the given options, only AA and aa are two contrasting traits whereas AA and Aa both express the same trait that is a dominant trait.
Thus, natural selection would act the most on AA and aa as they are contrasting traits (homozygous dominant and homozygous recessive).
