Use the Square Root Property to Solve the Equation $x ^ { 2 } + 81 = 0$

Multiple Choice

Use the square root property to solve the equation.
$x ^ { 2 } + 81 = 0$

A) $\{ 9 \}$
B) $\{ - 9,9 \}$
C) $\{ 6561 \}$
D) $\{ - 9 i , 9 i \}$