Correct Answer - Option 3 : isotope effect
Isotope effect: The importance of lattice vibrations suggest that an electron-phonon interaction is responsible for superconductivity. There is no reason for the superconducting transition temperature to depend on the number of neutrons in the nucleus.
Meissner effect: The expulsion of magnetic flux when a material becomes superconducting in a magnetic field.
Josephson effect: It is the flow of electric current between two pieces of superconducting material separated by a thin layer of insulating material.