In partition chromatography, which includes paper chromatography, the stationary phase is typically water held by cellulose fibers in the paper. This paper acts as an inert support. When a mixture is applied to the paper, its components partition between this stationary phase and the mobile phase (which can be a liquid or a gas). The varying affinities of the mixture's components for the stationary and mobile phases allow for their separation.

Now, let's address the options :

Option A : Mobile phase can be a gas - This is true. In partition chromatography, the mobile phase can be either a liquid or a gas.

Option B : Stationary phase is a finely divided solid adsorbent - This is typically false for partition chromatography. Here, the stationary phase is a liquid (like water in paper chromatography) that's held by an inert solid support (like cellulose paper).

Option C : Separation depends upon equilibration of solute between a mobile and a stationary phase - This is true. In partition chromatography, the mixture's components equilibrate between the mobile and stationary phases, leading to their separation.

Option D : Paper chromatography is an example of partition chromatography - This is true. As explained above, in paper chromatography, the stationary phase (water) is held by an inert support (cellulose paper), fitting the definition of partition chromatography.