The correct answer is option 'B', the total polarisation of a material is the sum of all types of polarisation. Let's understand this in detail:

Polarisation refers to the alignment of electric dipoles within a material in response to an external electric field. It is an important phenomenon in various electrical and electronic applications.

Different types of polarisation can occur in a material, and the total polarisation is the combined effect of all these types. Let's explore the different types of polarisation:

1. Electronic Polarisation:
- Occurs in materials with covalent or ionic bonds.
- In the presence of an external electric field, the electrons in the atoms or molecules get displaced, creating a temporary dipole moment.
- This displacement of electrons contributes to the overall polarisation of the material.

2. Ionic Polarisation:
- Occurs in ionic materials where there is a significant difference in electronegativity between the atoms.
- When an external electric field is applied, the positive and negative ions within the material get displaced in opposite directions, creating a dipole moment.
- This displacement of ions contributes to the overall polarisation of the material.

3. Orientation Polarisation:
- Occurs in materials with permanent dipoles, such as polar molecules or ferroelectric materials.
- In the absence of an external electric field, the dipoles within the material are randomly oriented.
- When an external electric field is applied, the dipoles align themselves in the direction of the field, resulting in a net dipole moment and polarisation.

4. Space Charge Polarisation:
- Occurs in materials with localized charges or defects.
- When an external electric field is applied, these localized charges or defects move, creating a net dipole moment and polarisation.

Now, the total polarisation of a material is the sum of these different types of polarisation. Each type contributes to the overall polarisation, and their effects are additive. Therefore, the correct answer is option 'B', which states that the total polarisation is the sum of all types of polarisation.

In summary, polarisation in a material arises from various mechanisms such as electronic polarisation, ionic polarisation, orientation polarisation, and space charge polarisation. The total polarisation is the combined effect of all these types, and it is important to consider their individual contributions when analyzing the behaviour of a polarised material.