Answer:
The correct answer is C. genetic drift
Explanation:
Genetic drift occurs in a small population due to the change in the allele frequency in a population due to random sampling. For example, in the bottleneck effect, most of the individual in the population die because of the natural calamities or disease which reduces the population size.
Therefore it this condition the small population have less genetic variation than the older big population because of loss of several allele due to killing of most individuals of the population in the calamity. Therefore the gene pool becomes small in smaller populations due to genetic drift. So the right answer is C. genetic drift.
