# If $P(0,1,0)\:and\:Q(0,0,1)$ are two points in space, then the projection of $PQ$ on the plane $x+y+z=3$ is ?
$\begin{array}{1 1} (a)\:\:2\:\:\:\qquad\:\:\\ (b)\:\:3\:\:\:\\ (c)\:\:\sqrt 2\:\:\: \\ (d)\:\:\sqrt 3. \end{array}$