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:
At what x-value(s) , if any, does the graph of f have a horizontal tangent?

A) x = -1 and x = 0
B) x = -2
C) x = -2, x = 1, and x = 0
D) x = -2 and x = 1
E) None