Superconductors show :

The correct answer is Option (1) → Perfect diamagnetism

When a metal is cooled below its critical temperature and becomes superconducting, it expels the magnetic field completely from its interior (the Meissner effect). Then \( B = 0 \) inside, so

    \( \displaystyle B = \mu_0 (1 + \chi) H = 0 \;\Rightarrow\; \chi = -1 \)

A susceptibility of \( -1 \) is the largest possible diamagnetic response, so a superconductor is a perfect diamagnet.

NCERT (2026-27):
Diamagnetism – “… The most exotic diamagnetic materials are superconductors. These are metals, cooled to very low temperatures which exhibits both perfect conductivity and perfect diamagnetism.”