Let f be twice differentiable, and suppose f′(c)=0 and f′′(c)>0. Which of the following statements best describes the behavior of f at x=c?
a) f has a local maximum at x=c.
b) No conclusion about local extrema can be drawn from this information.
c) f has a local minimum at x=c.
d) x=c is a point of inflection of f.