ANS:D - none of these.

The rate of mass transfer is dependent on both the degree of dispersion of one fluid in the other and the interfacial surface area exposed between the phases. Therefore, the correct answer is both (a) & (b). The degree of dispersion affects how effectively the two phases can interact and transfer mass, while the interfacial surface area determines the area over which mass transfer can occur. Both factors play crucial roles in determining the rate of mass transfer between phases in processes such as absorption, extraction, and distillation.