In the $Langmuir$ adsorption model,the adsorption of a gas on a solid surface is:

• A
  The amount of gas striking the given surface area is independent of the pressure of the gas.
• B
  The rate of desorption of adsorbed molecules from the surface does not depend on the surface covered.
• C
  The adsorption occurring on one side of the surface is assumed to be unimolecular at the same time.
• D
  The amount of gas striking the given surface area is inversely proportional to the pressure of the gas.