According to Margaret Davis, Who Studied Pollen Contained Within Lake $\rightarrow$

According to Margaret Davis, who studied pollen contained within lake sediments, the vegetation landscape of the Appalachian Mountains from 12,000 years ago until approximately 100 years ago changed as follows:

A) spruce $\rightarrow$ chestnut $\rightarrow$ beech.
B) chestnut $\rightarrow$ spruce $\rightarrow$ beech.
C) beech $\rightarrow$ spruce $\rightarrow$ chestnut.
D) spruce $\rightarrow$ beech $\rightarrow$ chestnut.
E) chestnut $\rightarrow$ beech $\rightarrow$ spruce.