A wire elongates by $\ell m m$ when a load $\mathrm{w}$ is hung from it. If the wire goes over a pulley and two weights $w$ each are hung at the two ends, the elongation of the wire will be (in mm)
(A) $\ell$
(B) $2 \ell$
(C) Zero
(D) $\frac{\ell}{2}$