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 down?

A) $( - \infty , 1 )$
B) $( - \infty , - 2 ) \cup ( 0 , \infty )$
C) (-2, 0)
D) $( 1 , \infty )$
E) (-2, 1)