A subset of a population of birds leaves its habitat and colonizes a nearby island. After many generations, the island sinks and the population of birds living on the island returns to its original habitat. Which of the following statements mostaccurately describes the two bird populations?

a. The birds were separated by dispersal.
b. The subset of a population of birds leaves its habitat and colonizes a nearby island.
c. After many generations, the island sinks and the population of birds living on the island returns to its original habitat.