Answer:
A. Birch trees accounted for 40% less of the forest's trees in 2000.
Explanation:
Between 1950 and 2000, birch trees began to be used a lot in the production of furniture, floors and plywood, which caused the specimens of this tree in the forests to decrease over time. This is because its wood makes it possible to manufacture a cheap and accessible material for the majority of the population, for this reason, birch trees represented 40% less than trees in the forest in 2000, when scientists analyzed the data of their research.