On what factor does the pole strength of a magnet depends?

The $\mathrm{B}-\mathrm{H}$ Curve of a ferromagnetic material is as shown in figure:

$\left(\mathrm{b}\right)$ Identify the value of retentivity and coercivity from the figure.

The $\mathrm{B}-\mathrm{H}$ Curve of a ferromagnetic material is as shown in figure:

A solenoid has a core of a material with relative permeability $400$. The windings of the solenoid are insulated from the core and carry a current of $2\mathrm{A}$. If the number of turns is $1000$ Per metre, calculate magnetic intensity $\left(\mathrm{H}\right)$ and magnetic field $\left(\mathrm{B}\right)$.

Which of the field pattern given below is valid for electric field as well as for magnetic field?

Assertion: The magnetic field lines are continuous and form closed loops.

Reason: Magnetic monopole does not exist.

The correct option among the following is

Assertion: It is not necessary that every magnet has one North pole and one South pole.

Reason: It is a basic fact that magnetic poles occur in pairs.