Three magnetic materials are listed below:

(A) Paramagnetics
(B) Diamagnetics
(C) Ferromagnetics
Choose the correct order of the materials in increasing order of magnetic susceptibility.

The correct option is (B), (A), (C).

Explanation:
Magnetic susceptibility ($\chi$) is a dimensionless parameter that indicates how easily a material becomes magnetized when placed in an external magnetic field. It is defined as the ratio of the magnetization ($M$) of the material to the applied magnetic field strength ($H$):

$\chi =\frac{M}{H}$

Let us look at the magnetic susceptibility values for each of the three types of materials:

1. Diamagnetic Materials (B):
Diamagnetic materials develop a weak magnetization in a direction opposite to the applied magnetic field. Consequently, their magnetic susceptibility is negative and small in magnitude.

${\chi }_{\text{diamagnetic}}<0$

Typically, the value of $\chi$ for diamagnetic materials is in the range of $-{10}^{-5}$ to $-{10}^{-9}$.

2. Paramagnetic Materials (A):
Paramagnetic materials acquire a weak magnetization in the same direction as the applied magnetic field. Therefore, their magnetic susceptibility is positive but small in magnitude.

${\chi }_{\text{paramagnetic}}>0$

Typically, the value of $\chi$ for paramagnetic materials is in the range of ${10}^{-5}$ to ${10}^{-3}$.

3. Ferromagnetic Materials (C):
Ferromagnetic materials acquire a very strong magnetization in the direction of the applied magnetic field. Their magnetic susceptibility is positive and exceptionally large.

${\chi }_{\text{ferromagnetic}}\gg 1$

Typically, the value of $\chi$ for ferromagnetic materials is on the order of ${10}^3$ to ${10}^5$.

Arranging in Increasing Order:
Comparing the values, we have:
Negative susceptibility < Small positive susceptibility < Large positive susceptibility
Therefore, the correct increasing order is:
Diamagnetics (B) < Paramagnetics (A) < Ferromagnetics (C)

This corresponds to the sequence: (B), (A), (C).