Which of the following populations is in genetic equilibrium?
Correct answer: B. AA: 0.25; Aa: 0.50; aa: 0.25
A population is in genetic equilibrium if the frequencies of alleles and genotypes remain constant from one generation to another, as described by the Hardy-Weinberg principle. The given genotype frequencies for option B (AA: 0.25; Aa: 0.50; aa: 0.25) satisfy this condition.