Ruby is aluminium oxide $\left({\mathrm{Al}}_2{\mathrm{O}}_3\right)$ containing about $0.5-1\mathrm{\%}{\mathrm{Cr}}^{3+}$ ions $\left({\mathrm{d}}^3\right)$, which are randomly distributed in positions normally occupied by ${\mathrm{AI}}^{3+}$ Choose the only incorrect statement :

d-d transitions at these centres give rise to colour

${\mathrm{Cr}}^{3+}$ is incorporated into the alumina lattice as octahedral chromium (III) complexes

The absorption bands seen in the Emerald, shift to longer wavelength, namely yellow-red and blue, causing Ruby to transmit light in green region.

In Emerald, ${\mathrm{Cr}}^{3+}$ + ions occupy octahedral sites in the mineral beryl $\left({\mathrm{Be}}_3{\mathrm{Al}}_2{\mathrm{Si}}_6{\mathrm{O}}_{18}\right)$