) (γ - nb) = nRT where, p = pressure V = volume n = no. of moles T = temperature a, b = Vander Waals' constant Constant 'a' measures the intermolecular force of attraction between the gas molecules whereas constant 'b' measures the effective size of the gas molecules As the value of 'b' is same. Gas having a larger value of 'a' will occupy lesser volume or gas having smaller value of 'a' will occupy larger volume. This is due to the fact that larger value of 'a' will have larger forces of attraction and therefore, the distance between its molecules will be less. Hence, option 'A' is correct.