The desirable properties for making permanent magnets are

Magnetic materials used for making permanent magnets $\left(\mathrm{P}\right)$ and magnets in a transformer $\left(\mathrm{T}\right)$ have different properties of the following, which property best matches for the type of magnet required?

Given below are two statements: one is labelled as Assertion $\mathbf{A}$ and the other is labelled as Reason $\mathbf{R}$.
Assertion A : Electromagnets are made of soft iron.
Reason R : Soft iron has high permeability and low retentivity.
In the light of above statements, choose the most appropriate answer from the options given below.

The $B-H$ curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid with $1000 \mathrm{turns} {\mathrm{cm}}^{-1}$. The current that should be passed in the solenoid to demagnetize the ferromagnet completely is, 

A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic substance. The whole system is placed in a uniform magnetic field $\overrightarrow{\mathrm{B}}$. Then the field inside the paramagnetic substance is: