At low pressures, the van der Waals' equation is written as $\left[\mathrm{p}+\frac{\mathrm{a}}{{\mathrm{V}}^2}\right]\mathrm{V}=\mathrm{RT}$

The compressibility factor is then equal to

• A

  $\left(1-\frac{\mathrm{a}}{\mathrm{RTV}}\right)$

• B

  $\left(1-\frac{\mathrm{RTV}}{\mathrm{a}}\right)$

• C

  $\left(1+\frac{\mathrm{a}}{\mathrm{RTV}}\right)$

• D

  $\left(1+\frac{\mathrm{RTV}}{\mathrm{a}}\right)$