Step 1: Concept In a ccp (or fcc) lattice, if the number of atoms is $N$, the number of tetrahedral voids is $2N$.
Step 2: Meaning Let the number of anions (B) be $N$. Then number of tetrahedral voids is $2N$.
Step 3: Analysis Cations (A) occupy $1/3$ of tetrahedral voids.
Number of A = $\frac{1}{3} \times 2N = \frac{2N}{3}$.
Ratio A : B = $\frac{2N}{3} : N = 2 : 3$.
Step 4: Conclusion The chemical formula is $\text{A}_2\text{B}_3$.
Final Answer: (B)