Answer: d. both a and b.
Step-by-step explanation:
Soaps are cleansing agents. These are composed of salts and fatty acids. The soaps functions as degerming agents and surfactants.
A surfactant is a molecule which consists of a lipophilic end which basically attracts the grease and dirt. The other end is the hydrophilic which makes the dirt and grease molecules dissolve in water. This way functions as important cleansing agent.
A degerming agent is the one which removes the microbes over the surface mechanically.
Thus soaps play dual role in cleansing as well as sterilization.