If the anions (A) form hexagonal closest packing and cations (C) occupy only 2/3 octahedral voids in it, then the general formula of the compound is
CA
CA2
C3A2
C2A3
We know that, there are 6 A ions that form the HCP lattice
The number of Octahedral void in HCP lattice = 6
Hence, the correct answer is Option (4)