The graph below shows a change in beak depth (beak size) of the medium ground finch over a period of years. Based on the theory of natural selection, which of the explanations best describes the change in the beak depth of the medium ground finch during the dry years?

A.
The beak size of an individual finch decreased during dry years due to the survival and reproduction of finches with beak sizes greater than 9.6 mm.

B.
The beak size of the finch population increased during dry years due to the survival and reproduction of finches with beak sizes greater than 9.6 mm.

C.
The beak size of an individual finch increased during dry years due to the survival and reproduction of finches with beak sizes greater than 9.6 mm.

D.
The beak size of the finch population decreased during dry years due to the survival and reproduction of finches with beak sizes greater than 9.6 mm.