For finches on the Galapagos, a significant change in beak size can be observed across years with plentiful rainfall or intense drought. How can the changes in finch beak size be attributed to evolution?

A) Finches on the island with better-adapted beak sizes have increased survival.
B) Finches on the island are domesticated and are artificially selected for beak size.
C) Finches on the island without well suited beak sizes change their diet to induce and enhance growth of their beaks.
D) Finches on the island reproduce with finches from nearby islands that have larger beaks, resulting in changing beak sizes over time.