If V is the volume of one molecule of a gas under given conditions, then van der Waals' constant b is

• A

  4V

• B

  $\frac{4\mathrm{V}}{{\mathrm{N}}_0}$

• C

  $\frac{{\mathrm{N}}_0}{4\mathrm{V}}$

• D

  $4{\mathrm{VN}}_0$