If the $B-H$ curves of two samples of $P$ and $Q$ of iron are as shown below,then which one of the following statements is $CORRECT$?

The figure shows the experimentally measured $B$ vs. $H$ variation in a ferromagnetic material. The retentivity,coercivity,and saturation of the material are,respectively:

The figure illustrates how $B$,the magnetic flux density inside a sample of unmagnetised ferromagnetic material,varies with $B_0$,the external magnetic flux density in which the sample is kept. For the sample to be suitable for making a permanent magnet:

If the $B-H$ curves of two samples $P$ and $Q$ of iron are as shown below,then which one of the following statements is correct?

The figure illustrates how $B$,the flux density inside a sample of unmagnetised ferromagnetic material,varies with $B_0$,the magnetic flux density in which the sample is kept. For the sample to be suitable for making a permanent magnet:

Answer the following questions:
$(a)$ Explain qualitatively on the basis of the domain picture the irreversibility in the magnetisation curve of a ferromagnet.
$(b)$ The hysteresis loop of a soft iron piece has a much smaller area than that of a carbon steel piece. If the material is to go through repeated cycles of magnetisation,which piece will dissipate greater heat energy?
$(c)$ '$A$ system displaying a hysteresis loop such as a ferromagnet,is a device for storing memory?' Explain the meaning of this statement.
$(d)$ What kind of ferromagnetic material is used for coating magnetic tapes in a cassette player,or for building 'memory stores' in a modern computer?
$(e)$ $A$ certain region of space is to be shielded from magnetic fields. Suggest a method.