$\text { Find all critical numbers of the function } g ( x ) = x ^ { 4 } - 4 x ^ { 2 } \text {. }$

Multiple Choice

$\text { Find all critical numbers of the function } g ( x ) = x ^ { 4 } - 4 x ^ { 2 } \text {. }$

A) critical numbers: $x = 0 , x = 2 \sqrt { 2 } , x = - 2 \sqrt { 2 }$
B) critical numbers: $x = 0 , x = \sqrt { 2 } , x = - \sqrt { 2 }$
C) critical numbers: $x = 2 \sqrt { 2 } , x = - 2 \sqrt { 2 }$
D) critical numbers: $x = \sqrt { 2 } , x = - \sqrt { 2 }$
E) no critical numbers