Which one of the following equations represents the Freundlich adsorption isotherm?

$2.0 \, g$ of $H_2$ gas is adsorbed on $2.5 \, g$ of platinum powder at $300 \, K$ and $1 \, bar$ pressure. The volume of the gas adsorbed per gram of the adsorbent is $..... \, mL$.
(Given: $R = 0.083 \, L \, bar \, K^{-1} \, mol^{-1}$)

If $x$ is the mass of the gas adsorbed on mass $m$ of the adsorbent at pressure $p,$ Freundlich adsorption isotherm gives a straight line on plotting

For the adsorption of a gas on a solid adsorbent,which of the following is positive?

Which of the following is not a characteristic of chemisorption?

Four gases $A$,$B$,$C$,and $D$ have critical temperatures $5.3 \ K$,$33.2 \ K$,$126.0 \ K$,and $154.3 \ K$ respectively. For their adsorption on a fixed amount of charcoal,the correct order is: