All the strong acids have very close pKa value and they appear to have nearly equal strengths in aqueous solutions. The phenomenon is called as

Explanation

The correct answer is Levelling effect. In aqueous solutions, all strong acids dissociate completely, making them appear to have equal strength. This phenomenon is called the levelling effect, where the solvent (water) sets a limit on the observable strength of the acids. The other options describe related concepts: a differentiating effect occurs in solvents that allow for partial dissociation, distinguishing between acid strengths, while levelling and differentiating solvents are terms related to the solvent's properties rather than the phenomenon itself.