Find All the Critical Numbers of the Function $f ( x ) = - 2 x ^ { 4 } + 4 x ^ { 2 } + 1$

Multiple Choice

Find all the critical numbers of the function $f ( x ) = - 2 x ^ { 4 } + 4 x ^ { 2 } + 1$ .

A) 0, 1, -1
B) -1
C) $\frac { 1 } { 2 }$
D) None