Both ZnS and CaF₂ Have a Face-Centered Cubic Unit Cell

Multiple Choice

Both ZnS and CaF₂ have a face-centered cubic unit cell where the S^2- and Ca²⁺ ions are closest packed in each structure .Which of the following is true?

A) There are 4 tetrahedral holes empty in each structure.
B) In both compounds, one-half of the tetrhedral holes are filled.
C) In both compounds, all the tetrhedral holes are filled.
D) In ZnS, one-half of the tetrahedral holes are filled by Zn²⁺ ions, whereas in CaF₂ all the tetrahedral holes are filled with F^- ions.
E) There are 8 Zn²⁺ ions and 4 F^- ions in the unit cell.