ANS:A - increases

With an increase in gas rate, the number of transfer units (NtoG) for a fixed degree of absorption by a fixed amount of solvent increases. The number of transfer units (NTU) is a measure of the efficiency of mass transfer in a system. In absorption processes, it represents the ratio of the actual amount of solute transferred to the amount that would be transferred if the system reached equilibrium. When the gas rate increases in an absorption process with a fixed amount of solvent and a fixed degree of absorption, it typically leads to enhanced mass transfer due to increased contact between the gas and liquid phases. This increased contact results in higher rates of solute transfer from the gas phase to the liquid phase. Consequently, the number of transfer units (NTU) increases as a result of the improved mass transfer efficiency.