The answer is D. Column chromatography has a mobile and stationary phase. The stationary phase is made of solid beads with pores of particular sizes depending on the mixture being processed. The mobile phase is usually a solvent that carries the mixture down the column as the different components of the mixtures separate. The different elements, due to differences in sizes of their molecules, pass through the pores of the beads at different rates hence elute from the columns differentially.
