A differentiable function g is defined on an open interval containing x=5. The derivative satisfies g′(x)>0 for x<5 and g′(x)<0 for x>5. Which statement about g at x=5 is true?
a) g has a relative minimum at x=5.
b) g has a relative maximum at x=5.
c) g has a point of inflection at x=5.
d) g is increasing at x=5 because g′(5)>0.