What is the role of desorption in the process of catalysis?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: In expensive scientific instruments,silica gel is kept in watch-glasses or in semipermeable membrane bags.
Reason $(R)$: Silica gel adsorbs moisture from air via adsorption,thus protects the instrument from water corrosion (rusting) and/or prevents malfunctioning.
In the light of the above statements,choose the correct answer from the options given below:

$A$ mixture of substances $A, B, C, D$ is subjected to column chromatography. The degree of adsorption is in the order of $D > B > C > A$. The column is eluted with a suitable solvent. Identify the correct statement with respect to the separation of the mixture.

The substance used to decolourise and purify oils is

At high pressure,the entire surface is covered by a unimolecular layer of gas,which follows ......... order.

$A$ gas undergoes physical adsorption on a surface and follows the given Freundlich adsorption isotherm equation $\frac{x}{m} = k p^{0.5}$. Adsorption of the gas increases with