Which one of the following statements is true?

AIf f ′′(x) > 0 on the interval (a, b) then f(x) is concave down on the interval (a, b).

BIf f ′(x) > 0 on the interval (a, b) then f(x) is increasing on the interval (a, b).

CIf f ′(c) = 0, then x = c is a relative maximum on the graph of f(x).

DNone of these are true.