Let $y = f ( x )$ Be a Differentiable Function for Which the Graph of Its

Multiple Choice

Let $y = f ( x )$ be a differentiable function for which the graph of its derivative, ƒ ', is given below:
On what interval(s) is the graph of f concave up?

A) $( - \infty , 0 )$
B) (-3, 3)
C) $( 0 , \infty )$
D) $( - \infty , - 3 ) \cup ( 3 , \infty )$
E) $( - \infty , \infty )$