When Darwin studied the finches on the Galapagos Islands, he was able to observe the varying sizes of the finch beaks. Which of the following explains the beak size and shape in relation to the environment? a
The beak changed in size and depth only during the lifetime of the fittest birds able to survive the drought.

b
The beaks of individual birds in the population changed size and shape between the time of fledging the nest and adulthood, due to the environmental stress induced by drought.

c
The beak size and shape had corresponding genetic codes in the DNA that were modified or mutated by individuals when attempting to survive the stressful environment of the drought.

d
The beak size and shape varied across the population and sometimes conferred benefits in feeding, survivorship, and reproduction that were passed down to surviving offspring.