The correct option is (a) 6 x 1022.
We know that, in a body centred cubic unit cell the atoms/ molecules are present at the corners of the cell and one at the centre of the cell. So, the number of atoms/ molecules present in a body centred cubic lattice is n = 2
Using the formula for density,
Now we have the molecular mass of the given substance and so, we can find the number of atoms present easily by finding the number of moles in 2.4 g of the substance.
Moles = 2.4/24 = 0.1 mole
Thus, the number of atoms is given by
N = 0.1 × NA = 0.1 × 6.022 × 1023
N = 6.022 x 1022