Which of the following provides the best example of selective breeding?
A. Scientists have noted that different varieties of birds on different Islands have beaks that are suited to the birds available food,
B. Leopard seals captured in Antarctica have thicker layers of blubber than harbor seals captured in the Pacific Ocean
C. Hummingbirds have a long, narrow beak that enables them to reach food in the deepest parts of a flower
D. Racehorses that run fastest are the ones that are allowed to produce offspring, leading to faster racehorses.