ANS:A - increases

For a fixed number of ideal stages in a distillation column, as the reflux ratio is increased, the difference in composition between the top and bottom product streams typically increases. The reflux ratio is the ratio of the liquid returned to the top of the column (reflux) to the liquid withdrawn as product from the bottom of the column. Increasing the reflux ratio means sending more liquid back to the column's upper stages, increasing the liquid holdup in the column. This increased liquid holdup allows for more equilibrium stages, leading to improved separation efficiency. As the reflux ratio increases, more of the lighter components are condensed and returned to the column's upper stages. This results in a higher concentration of lighter components in the distillate (top product) and a lower concentration of lighter components in the bottoms product. Therefore, the difference in composition between the top and bottom product streams increases as the reflux ratio is increased.