7. Retention factor.sctor, Re describes R_(2) A. The stationary and the mobile phase B. The migration rate of an analyte through a column C. The velocity of the mobile phase D. All of the above

The correct answer is B. The migration rate of an analyte through a column.<br /><br />The retention factor, denoted as $R_{2}$, is a measure of how long an analyte remains in the column relative to the time it takes for the solvent to pass through the column. It is calculated as the ratio of the time the analyte spends in the column to the time the solvent takes to pass through the column. This value provides information about the interaction between the analyte and the stationary phase in the column.