In Freundlich adsorption isotherm at moderate pressure, the extent...

Freundlich gave a relation between the amount of the gas adsorbed per unit mass of the adsorbent (m) and the pressure (p). This is known as Freundlich’s adsorption isotherm.

As per Freundlich adsorption isotherm

$\left(\dfrac{x}{m}\right) = KP\dfrac{1}{n} \to x = \dfrac{1}{n}$

Hence answer is \left(2\right)