In column Chromatography, the moving phase is:
(A) The substances which are to be separated
(B) Eluent
(C) Adsorbent
(D)Mixture of eluent and substances to be prepared.

Hint: Column chromatography method used to isolate a single chemical compound from a mixture. Chromatography is used to separate substances based on differential adsorption of compounds to the adsorbent. Compounds move through the columns allowing them to be separated into fractions by the difference in their rates.

Complete step by step solution:
-When the mixture that needs to be separated is introduced from the top of the column, the movement of the individual components of the mixture is at different rates.
-The components with lower adsorption and affinity to stationary phase travel faster when compared to the greater adsorption and affinity with the stationary phase.
-The components that are fast are removed first whereas the components that are slow are eluted out last.
-The adsorption of solute molecules to the column occurs in a reversible manner that is repeated ever after completion. The rate of the movement of the components is expressed as:
$\mathrm{R}_{\mathrm{f}}=$ the distance travelled by solute/ the distance travelled by the solvent
$\mathrm{R}_{\mathrm{f}}$ is the retardation factor.
 -Now, let us discuss the moving phase:
It is a mixture of the eluent and the substances to be prepared.
It acts as a solvent where the sample mixture can be introduced in the column.
It acts as a developing agent which helps in the separation of components in the sample to form bands.
It acts as an eluting agent where the components that are separated during the experiment are removed from the column

Hence, the answer is option (B).

Note: The polarity of the solvent which is passed through the column affects the relative rates at which compounds move through the column. Polar solvents can effectively go through with the polar molecules of a mixture for the polar sites on the adsorbent surface and will also better solvate the polar molecules.