Which describes the concavity of the function f(x) = (x² - 1) / eˣ, -2.5?
A. Concave upward in (-2.5, 1) and concave downward in (1, 2.5)
B. Concave downward in (-2.5, 1) and concave upward in (1, 2.5)
C. Concave upward in (-2.5, 0.27) and concave downward in (0.27, 2.5)
D. Concave downward in (-2.5, 0.27) and concave upward in (0.27, 2.5)