In the Unit Cell of Sphalerite, Zn²⁺ Ions Occupy Half

Multiple Choice

In the unit cell of sphalerite, Zn²⁺ ions occupy half the tetrahedral holes in a face-centered cubic lattice of S^2- ions. What is the number of formula units of ZnS in the unit cell?

A) 3
B) 5
C) 4
D) 1
E) 2