Solve the Equation by Making an Appropriate Substitution $$x ^ { 4 } - 2 x ^ { 2 } - 8 = 0$$

Multiple Choice

Solve the equation by making an appropriate substitution.
- $$x ^ { 4 } - 2 x ^ { 2 } - 8 = 0$$

A) $\{ 2 , i \sqrt { 2 } \}$
B) $\{ - 4,2 \}$
C) $\{ - 2,2 , - \mathrm { i } \sqrt { 2 } , \mathrm { i } \sqrt { 2 } \}$
D) $\{ - \sqrt { 2 } , \sqrt { 2 } , - 2 i , 2 i \}$