At x=2, a differentiable function f satisfies f′(2)=0 and f′′(2)<0. Which of the following statements about f at x=2 is true?
a) The graph of f has a relative minimum at x=2.
b) The function f is increasing at x=2.
c) The graph of f has a relative maximum at x=2.
d) The point x=2 is a point of inflection of f.