Adsorption of a gas on solid metal surface is spontaneous and exothermic, then

Adsorption of a gas on solid metal surface is spontaneous and exothermic in nature. It is physical adsorption. It is also known as physisorption. Being spontaneous and exothermic in nature, ∆G and ∆H are negative.

Recalling the expression:

 $\mathrm{\Delta G}=\mathrm{\Delta H}-\mathrm{T\Delta S}$

For, ∆G and ∆H are negative, $∆\mathrm{S}=-\mathrm{ve}.$

Therefore, option D is correct.