Correct choice is (c) bands
To explain I would say: pKa is the pH at which half the groups are ionized. Retention time is the time at specific analytes elute out. Peaks are formed as result in chromatographs. Peaks and retention time is seen during HPLC. In FPLC, the sample is introduced and carried into the column by the mobile phase. As the solvent is forced by the flow rate, the sample separates into various zones of sample components and is referred to band.