Answer:
The correct answer would be A. The population is evolving.
The allele frequency of a gene in a population remains constant generations over generations in absence of evolutionary factors such as selective mating, genetic drift, natural selection et cetera.
If the allele frequency of the gene for brown fur has increased from 15 percent to 25 percent, then it must be providing some survival advantage to the population due to which nature would select and complement the survival of organisms with brown fur.
Thus, the population of a beer would be evolving so as to have better adaptations against changing environments.
