Which of the following is most suitable for the core of electromagnets?

$A$ diamagnetic material in a magnetic field moves:

For two types of magnetic materials $A$ and $B$, the variation of $\frac{1}{\chi}$ ($\chi$: magnetic susceptibility) versus temperature $T$ is shown in the figure. Then:

$A$ thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on,the diamagnetic rod is pushed up,out of the horizontal magnetic field. Hence,the rod gains gravitational potential energy. The work required to do this comes from:

$A$ sensitive magnetic instrument can be shielded very effectively from outside magnetic fields by placing it inside a box of

Statement $I :$ The ferromagnetic property depends on temperature. At high temperature,a ferromagnet becomes a paramagnet.
Statement $II :$ At high temperature,the domain wall area of a ferromagnetic substance increases.
In the light of the above statements,choose the most appropriate answer from the options given below :