#### Answer

$C$

#### Work Step by Step

Subtract $5$ to both sides of the equation to obtain:
$x^2=-5$
Take the square root of both sides to obtain:
$\sqrt{x^2}=\pm \sqrt{-5}
\\x = \pm \sqrt{(-1)5}$
Since $\sqrt{-1}=i$, then the expression above simplifies to
$x=\pm i\sqrt5$
Thus, the answer is $C$.