The correct option is (a) solvent polarity
For explanation: Due to the organic phase in biphasic system, the most important factor in the balance between stabilization and inactivation is solvent polarity. Lower solvent polarity has lesser capacity to disrupt the structure of the necessary tightly bound water molecules. The best measure of solvent polarity is the logarithm of the partition coefficient. For the use of biphasic systems in many enzyme-catalyzed reactions, the important factor to be addressed is stability of the enzyme. Inactivation of enzyme may occur when the enzyme-bound water is diluted by the use of the more water-soluble organic solvents.