Let h(x)=x1/3. The derivative h′(x) is undefined at x=0. Which statement about x=0 is most accurate?
a) x=0 is a local maximum because h′(0) is undefined and h′′(x)<0 on both sides of 0.
b) x=0 is a local minimum because h(0)=0 and h(x)≥0 for all real x.
c) x=0 is neither a local maximum nor a local minimum because h(x) increases on both sides of 0.
d) x=0 is the global maximum of h because the function is unbounded below as x→−∞.