Most Marine Turtles in a Small Population Have Six Large

Most marine turtles in a small population have six large scales down the centre of their carapace; however, in each generation, a few have seven. Every year, females of a population of marine turtles come ashore to lay their eggs on a small coral atoll. Some turtles bury their eggs in 'nests' that they dig in the sand, just above the high-tide mark, while others dig their nests further inland. The females return to the sea immediately after burying their eggs and the eggs incubate in the sand for about 8 weeks. In one season, heavy seas accompanying a cyclone destroy 85 per cent of all turtle nests on the island. Some years later it is observed that very few turtles lay their eggs just above the high-tide mark; most lay their eggs well inland. It is also observed that the majority of the nesting females have seven central carapace scales.
The change in carapace morphology of the population is most likely the result of

A) natural selection.
B) neutral selection.
C) genetic drift.
D) environmental adaptation.
E) Based on this information, it is impossible to say.