In eastern gray squirrels, Sciurus carolinensis, the allele for black fur (B) is dominant to the allele for gray fur (b). In a particular population of gray squirrels, 64% have black fur and 36% have gray fur. A researcher calculated the allelic frequencies to be B = 0.4 and b =0.6. Five years later, the researcher returned to the location and determined the allelic frequencies within the squirrel population to be B = 0.6 and b = 0.4. Which of the following could best explain the increase in the frequency of the Ballele in the population after five years?
(A) The frequency of the B allele increased because it is the dominant allele.
(B) The frequency of the Ballele increased because squirrels with gray fur exhibited greater fitness.
(C) The frequency of the B allele increased due to the selective pressures of the environment.
(D) The frequency of the Ballele increased because black squirrels randomly mate with other eastern gray squirrels.