The total number of octahedral void(s) per atom present in a cubic close packed structure is:
(AIPMT 2012)

The correct option is B $1$
In a fcc/ccp unit cell:
Octahedral voids location:
1 at body centre and 12 voids at edge centres
$\text{Contribution for voids at edges is}\frac{1}{4}$
$\text{Contribution for body centre void is}1$

$\text{Total octahedral voids}:1+12\times \frac{1}{4}=4$
There are 4 octahedral voids per unit cell.

There are 4 atoms in each fcc unit cell.

Thus, the total number of octahedral void(s) per atom present in a cubic close packed structure is one.

Hence, option (c) is correct.