What is the equation form of Langmuir isotherm under high pressure ?

Question

$(a)\;\large\frac{x}{m}=\large\frac{a}{b}\qquad(b)\;\large\frac{x}{m}=ap\qquad(c)\;\large\frac{x}{m}=\large\frac{1}{abp}\qquad(d)\;\large\frac{x}{m}=\large\frac{b}{a}$