ANS:A - - ve

When both fluids flow concurrently in an absorber, the slope of the operating line is typically negative (- ve). Here's why:

• In concurrent flow, the gas phase and liquid phase flow in the same direction through the absorber.
• The operating line represents the relationship between the compositions of the gas and liquid phases at each stage of the absorber.
• In absorbers, the gas phase typically contains the solute to be absorbed, while the liquid phase is the absorbent.
• As the solute is absorbed from the gas phase into the liquid phase, the concentration of the solute decreases in the gas phase while it increases in the liquid phase.
• Therefore, as we move along the operating line from bottom to top (representing the stages of the absorber), the gas phase composition decreases while the liquid phase composition increases.
• This results in a negative slope for the operating line.