Point out the incorrect statement

Question

(a) Adsorption may or may not involve  the formation of bond between adsorbent and adsorbate.

(b) At high pressure, the Freundlich isotherm acquires a form $\frac{x}{m} \propto p$

(c) Physisorption involves formation of multimolecular layers.

(d) Adsorption involves the concentration of one substance over the surface of other.