The most accurate response that illustrates the correlation between a specific trait (the shape of a finch's beak) and competitive advantage in a particular environment is:
Only individuals that had beaks well-adapted to eat food resources found on an island survived and reproduced on that island.
This statement emphasizes the idea of natural selection, where the beak shape directly correlates with the finches' ability to access available food resources, leading to their survival and reproductive success in the specific environment of the Galápagos islands.