Find the X Coordinates of All Relative Extreme Points Of f

Multiple Choice

Find the x coordinates of all relative extreme points of $f ( x ) = \frac { 1 } { 2 } x ^ { 4 } - \frac { 2 } { 3 } x ^ { 3 } - 6 x ^ { 2 } - 100$

A) x = -2, 0, 3
B) x = 0
C) x = -3, 0, 2
D) x = -3, 2
E) x = -2, 3