An element occurring in the $bcc$ structure has $12.08 \times 10^{23}$ unit cells. The total number of atoms of the element in these cells will be

In a $bcc$ unit cell, the number of atoms per unit cell is $2$. So total atoms are $$2 \times 12.08 \times 10^{23}$$ $$24.16 \times 10^{23}$$ On checking the options, this matches option $D$.