Which of the following is the correct expression for the equation of state of van der Waals gas?
\((a)\,\left(P+\frac{a}{n^2V^2}\right)(V-nb)=nRT\)
\((b)\,\left(P+\frac{na}{n^2V^2}\right)(V-nb)=nRT\)
\((c)\,\left(P+\frac{an^2}{V^2}\right)(V-nb)=nRT\)
\((d)\,\left(P+\frac{n^2a^2}{V^2}\right)(V-nb)=nRT\)
