I believe the answer would be B. someone correct me if I'm wrong.
Genetic drift occurs when there is no random mating across a population. This causes a change in allelic frequency due to a random sampling of the population.
As the aboriginal population explored the earth, a small part of the population became geographically isolated either due to continental drift and climate changes. As the isolated population grew bigger, they established their own gene pool. This resulted a change in genotypic frequencies from that of the aboriginal population.
Your answer would be D. You can find the neutrons by subtracting the mass by the atomic number. 14-6=8 neutrons.