The van der Waals equation of state for a real gas is given. For $n$ moles of a real gas,the equation can be expressed as:

• A
  $\left( {\frac{P}{n} + \frac{{na}}{{{V^2}}}} \right)\left( {\frac{V}{{n - b}}} \right) = RT$
• B
  $\left( {P + \frac{a}{{{V^2}}}} \right)(V - b) = nRT$
• C
  $\left( {P + \frac{{na}}{{{V^2}}}} \right)(nV - b) = nRT$
• D
  $\left( {P + \frac{{{n^2}a}}{{{V^2}}}} \right)(V - nb) = nRT$