Superconductors have-
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → zero resistivity.
Resistivity (ρ) measures how strongly a material opposes the flow of current; conductivity (κ) is its reciprocal, κ = 1/ρ. Superconductors are materials that, by definition, have zero resistivity, that is infinite conductivity. Earlier only metals and alloys at very low temperatures (0 to 15 K) were known to behave in this way; now some ceramic materials and mixed oxides are superconducting at temperatures as high as about 150 K.
Why the other options are incorrect
Option (1) finite conductivity. — Incorrect. Ordinary conductors such as copper have a finite conductivity; a superconductor’s conductivity is infinite.
Option (2) infinite resistivity. — Incorrect. Very high resistivity is the property of an insulator, the opposite of a superconductor.
Option (4) zero conductance. — Incorrect. Zero conductance would mean no current flows at all, which again describes an insulator.
NCERT (2026-27 edition):
Conductance of Electrolytic Solutions – “… Certain materials called superconductors by definition have zero resistivity or infinite conductivity. Earlier, only metals and their alloys at very low temperatures (0 to 15 K) were known to behave as superconductors, but nowadays a number of ceramic materials and mixed oxides are also known to show superconductivity at temperatures as high as 150 K.”