Find the value of $x$ for which $x(\hat i + \hat j +\hat k)$ is a unit vector.

Question

$\begin{array}{1 1} (A) x = \pm \large\frac{1}{\sqrt 3} \\ (B) x = \pm \large\frac{1}{3} \\ (C) x = \pm 1 \\ (D) x = \pm 3\end{array}$