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

Question

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