Find the unit vector in the direction of vector $ \overline{PQ}$, where $P$ and $Q$ are the points $(1, 2, 3)$ and $(4, 5, 6)$ respectively.

Question

$\begin{array}{1 1}(A) \large\frac{1}{3}\hat i+\large\frac{1}{3}\hat j+\large\frac{1}{3}\hat k \\ (B) \large\frac{1}{\sqrt 3}\hat i+\large\frac{1}{\sqrt 3}\hat j+\large\frac{1}{\sqrt 3}\hat k \\ (C) 3\hat i+3\hat j+3\hat k \\(D) \sqrt 3\hat i+\sqrt 3\hat j+\sqrt 3\hat k \end{array} $