At low pressure Van der Waal's equation is reduced to $[P+\large\frac{a}{V^2}]V = RT$ The compressibility factor can be given as

Question

$(a)\;1-\large\frac{a}{RTV}\qquad(b)\;1-\large\frac{RTV}{a}\qquad(c)\;1+\large\frac{a}{RTV}\qquad(d)\;1+\large\frac{RTV}{a}$