Solve the Equation in the Real Number System $x ^ { 4 } - 21 x ^ { 2 } - 100 = 0$

Multiple Choice

Solve the equation in the real number system.
- $x ^ { 4 } - 21 x ^ { 2 } - 100 = 0$

A) $\{ - 5,5 \}$
B) $\{ - 5 , - 2,2,5 \}$
C) $\{ - 10,10 \}$
D) $\{ - 2,2 \}$