Let $f ( x ) = x ^ { 3 } - x + 2$

Multiple Choice

Let $f ( x ) = x ^ { 3 } - x + 2$ on $[ - 1,1 ]$ Then the set of all c in (-1,1) guaranteed by Rolle's Theorem is

A) $\left\{ \frac { - \sqrt { 3 } } { 3 } \right\}$
B) $\left\{ \frac { \sqrt { 3 } } { 3 } \right\}$
C) $\left\{ \frac { - \sqrt { 3 } } { 3 } , \frac { \sqrt { 3 } } { 3 } \right\}$
D) $\{ - 1,1 \}$
E) $\{ 1 \}$