Let f(x) and g(x) be two functions which are defined and differentiable for all x>x0. If f(x0)=g(x0) and f′(x)>g′(x) for all x>x0, then
a. f(x)<g(x) for some x>x0
b. f(x)=g(x) for some x>x0
c. f(x)>g(x) only for some x>x0
d. f(x)>g(x) for all x>x0