Let g be a function such that g(-1) = 0 and g(2) = 5. Which of the following conditions guarantees that there is an x, -1 < x < 2, for which g(x) = 3?
A) The function g is continuous on the interval [-1, 2].
B) The function g is differentiable on the interval [-1, 2].
C) The function g is strictly increasing on the interval [-1, 2].
D) The function g is concave up on the interval [-1, 2].