The correct order of density is:
\( \text{Be} > \text{Mg} > \text{Ca} > \text{Sr} \)
\( \text{Sr} > \text{Ca} > \text{Mg} > \text{Be} \)
\( \text{Sr} > \text{Be} > \text{Mg} > \text{Ca} \)
\( \text{Be} > \text{Sr} > \text{Mg} > \text{Ca} \)