The stationary phase in paper chromatography is-
[A] solid
[B] Organic solvent
[C] Water
[D] Paper

HINT: Paper chromatography is used to separate ions contained in a mixture. Here, two phases are present- mobile phase and stationary phase. Mobile phase is generally an organic solvent dominated mixture and the stationary phase consists of a polar solvent.

COMPLETE STEP BY STEP SOLUTION: Paper chromatography is a method, generally used in analytical chemistry, used to separate coloured chemicals or compounds.
It is a technique used for separation of different parts of a mixture of gases or liquids.
Paper chromatography has a few variants-
The first variant and the common variant is generally used in laboratories for teaching purposes and also for separating mixtures of compounds having similar polarity. This is the two dimensional variant which has two solvents and a piece of paper, hanged inside the chromatography chamber at an angle of${{90}^{\circ }}$.
In this two dimensional chromatography, there is a mobile phase and a stationary phase.
The mobile phase has a mixture of organic solvents which travels up due to capillary action. Capillary action is the ability of liquids to move upward, opposing the force of gravity. The organic solvents used in this phase are non-polar.
The stationary phase is a polar solvent like water. Water is used as the stationary phase because water molecules are held inside the voids of the paper.
A similar method like paper chromatography is thin layer chromatography where the only difference is the stationary phase.
Stationary phase in paper chromatography is water where as in thin layer chromatography adsorbent like silica gel or aluminium oxide is used.

Therefore, the correct answer is option [C] Water.

NOTE: The stationary phase is fixed and the mobile phase allows rising up to two-third level of the paper with the ions in it. No solid is used in the process and organic solvent is used in the mobile phase. Therefore, the correct answer is water.