Solve the Equation by Making an Appropriate Substitution $$2 x ^ { 1 / 2 } - 3 x ^ { 1 / 4 } - 20 = 0$$

Multiple Choice

Solve the equation by making an appropriate substitution.
- $$2 x ^ { 1 / 2 } - 3 x ^ { 1 / 4 } - 20 = 0$$

A) $\left\{ 4 , - \frac { 5 } { 2 } \right\}$
B) $\left\{ 256 , \frac { 625 } { 16 } \right\}$
C) $\{ - 4 , - 5 \}$
D) $\{ 256 \}$