Let $f ( x ) = \frac { 1 } { 2 } x ^ { 3 } - 3 x ^ { 2 } + 6 x - 4$

Multiple Choice

Let $f ( x ) = \frac { 1 } { 2 } x ^ { 3 } - 3 x ^ { 2 } + 6 x - 4$ The set of all critical numbers of ƒ is

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