Adsorption

In physisorption, also known as physical adsorption, the adsorbate is held to the adsorbentby weak forces like van der Waals forces of attraction. 

The extent of physisorption, or the amount of adsorbate adsorbed onto the surface, increases with a decrease in temperature. 

• This is because as the temperaturedecreases, the kinetic energy of the adsorbate molecules also decreases, allowing them to more easily adsorb onto the surface of the adsorbent.
• In contrast, when the temperature increases, the kinetic energyof the adsorbate molecules increases, making it more difficult for them to adsorb onto the surface of the adsorbent. 
• This leads to a decrease in the extent of physisorption.

Therefore, the extent of physisorption increases with a decrease in temperature due to the decrease in kinetic energy of the adsorbate molecules, which allows them to more easily adsorb onto the surface of the adsorbent.

Hence, option D is the correct answer.