The Van Der Waals Equation for Real Gases Contains an a Parameter

The van der Waals equation for real gases contains an a parameter and a b parameter. Which statement about these parameters is not correct?

A) One of these parameters accounts for the fact that the molecules occupy space and thereby reduce the free volume of the container.
B) One of these parameters accounts for the fact that attractive forces between the molecules serve to reduce the pressure exerted on the walls of the container.
C) The van der Waals equation is defined so both of these parameters have negative values.
D) Both of these parameters increase with increasing number of atoms in each molecule.
E) Both of these parameters increase with increasing mass of the molecules.