Selected values of the first derivative of a twice-differentiable function f are given.
x −2 −1 0 1 2
f'(x) −3 −1 0 −1 −3
Which statement is best supported by the data?
a) f has a local maximum at x=0
b) f is concave up on (1,2)
c) f has a point of inflection at x=0
d) f has a local minimum at x=0