Answer:
Option A
Explanation:
Oxide ions are at ccp position, hence 4O2- ions, Also there are four octahedral voids and eight tetrahedral voids. Since 'm' fraction of octahedral voids contain Al3+ and 'n' fraction of tetrahedral voids contain Mg2+ ions, to maintain electroneutrality 2(2Al3+=+6 charge) and (Mg2+= +2 charge ), will make unit cell neutral
Hence : m= $\frac{2}{4}=\frac{1}{2}$, n=$\frac{1}{8}$