Let $f ( x ) = x ^ { 3 } - 12 x + 1$

Multiple Choice

Let $f ( x ) = x ^ { 3 } - 12 x + 1$ The set of all critical numbers of ƒ is

A) $\{ - 2 \}$
B) $\{ 2 \}$
C) $\{ - 2,2 \}$
D) $\{ 0 , - 2 \}$
E) $\{ 0,2 \}$