The Van der Waals' equation for n moles of a gas is: (p+
n2a
V2
) (V - nb) = nRT where, p = Pressure V = Volume n = No. of moles R = Gas constant T = Temperature a, b = van der waals' constant where, 'a' is a constant which measures the forces of attraction between the molecules of a gas and 'b' is a constant that relates to incompressible volume of the molecules and measures effective size of the gas molecules. Hence, option 'A' is correct.