In a crystalline solid, anion y are arranged in cubic closed packing. Cation x are equally distributed between octahedral and tetrahedral voids. If all the octahedral voids are occupied, the chemical formula of the solid is 

y form ccp.

let no. of y is n.

⇒ no of octahedral voids = n
 

no. of tetrahedral voids =2n.

but cation x is equally distributed in Octahedral. 8 tetrahedral voids as all Oct. voids are occupied 

80   cation x is distributed as n + n (  Octahedral + tetrahedral)

$\frac{Y}{X}=\frac{1n}{2n}$

B:A::1:2          
Formula is $x_{2}y$.

Hence, option 2 is correct.