ANS:A - plug

The ratio of Murphree plate efficiency to point efficiency is always > 1 in a perfectly mixed flow model. In a perfectly mixed flow model, the liquid and vapor phases are thoroughly mixed at each stage of the distillation column. This results in a more uniform concentration gradient across the column compared to other flow models. As a result, the Murphree plate efficiency, which accounts for vapor-liquid equilibrium at each stage, tends to be higher than the point efficiency, which only considers the composition at a single point within the stage. Therefore, the correct option is: perfectly mixed