Correct Answer  Option 2 : 0.74
Explanation:
Atomic Packing Factor:
Packing factor is the fraction of the volume of a unit cell that is occupied by "hard sphere" atoms or ions.
It is the sum of the sphere volumes of all atoms within a unit cell (assuming the atomic hard  sphere model) divided by the unit cell volume (total volume).
The atomic packing factor of different crystal structures is given in the table below:
Structure

Atomic packing factor

BCC

0.68

HCP

0.74

FCC

0.74

Diamond cubic

0.34

SC

0.52
