In antifluorite structure, the negative ions:
Are arranged in ccp
Occupy tetrahedral voids
Are arranged in hcp
Occupy octahedral voids
As we have learnt,
Na2O (Anti-Fluorite Structure)
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In antifluorite crystal i.e Na2O, the anions are arranged in cubic close packing while the cations occupy all the tetrahedral voids.
Therefore, Option(1) is correct