What adaptations did Charles Darwin notice in the finches of the Galapagos Islands that helped him develop his theory of evolution by natural selection?
A. All of the finches looked the same regardless of the island from which they came.
B. The finches had the same beak sizes and shapes as the mainland finches.
C. The finches had gone extinct from the islands due to volcanic activity.
D. The finches had beaks of different sizes and shapes that were suited to the available food.
