Final answer:
In Hardy-Weinberg equilibrium, both allele and genotype frequencies remain constant (option C), which is true only if five conditions are met: no mutation, no migration, very large population size, random mating, and no natural selection.
Step-by-step explanation:
When a population is in Hardy-Weinberg equilibrium, certain conditions are met that result in both allele frequencies and genotype frequencies remaining constant from generation to generation. This means that under the Hardy-Weinberg principle, option C) Both A and B is the correct answer to what must be true about allele and genotype frequencies. Allele frequencies in a population will stay the same in the absence of evolutionary forces such as natural selection, mutation, genetic drift, and migration (gene flow). Moreover, when no evolutionary forces are at play, the genotype frequencies will also remain constant and can be determined using the Hardy-Weinberg equation.
To remain in the Hardy-Weinberg equilibrium, a population must satisfy these five conditions: no mutation, no migration, very large population size, random mating, and no natural selection. If these conditions are met, the population does not evolve, and both allelic and genotype distributions remain stable across generations.