ANS:D - Packed

The correct answer is packed column. In gas absorption processes, packed columns are commonly used. These columns are filled with packing materials such as rings, saddles, or structured packing. The packing provides a large surface area for intimate contact between the gas phase containing the solute to be absorbed and the liquid phase (absorbent). This facilitates the transfer of the solute from the gas phase to the liquid phase, resulting in efficient absorption.