According to the theory of natural selection, what factor below contributed to the current variations in beak sizes of finch species on the Galapagos Islands? a. Finches dispersed to islands where their beak sizes closely matched available seed sizes b. Different finch populations needed to change in order to survive, so beneficial new traits arose c. Non-heritable variation between individual was important for natural selection to work d. Genetic drift allowed beneficial traits to spread throughout the population e. Seeds are limited resource.