Ans: D
$\begin{array}{cl}
& h\ell -k\ell + hm – km -hn + kn \\
= & \ell(h-k) +m (h-k) -n(h-k) \\
= & (h-k)(\ell +m – n)
\end{array}$
$\begin{array}{cl}
& h\ell -k\ell + hm – km -hn + kn \\
= & \ell(h-k) +m (h-k) -n(h-k) \\
= & (h-k)(\ell +m – n)
\end{array}$
