Explanation:

- Sanskritisation refers to the process where lower castes adopt the customs, rituals, and practices of upper castes, especially Brahmins, to improve their social status.

- In the context of Hindu tradition, this process is seen as a unique historical way in which Indian society has changed over time.

Option 1: Diffusion

- Diffusion means the spread of cultural elements from one group to another.

- Sanskritisation involves spread, but it is more about changing identity, not just sharing elements.

Option 2: Accommodation

- Accommodation is when different groups adjust to each other without losing their core identity.

- Sanskritisation is about adopting, not just adjusting.

Option 3: Assimilation

- Assimilation is when one group fully adopts another group's culture, losing their original identity.

- Sanskritisation is partially like assimilation, but groups often keep some original traits.

Option 4: Acculturation

- Acculturation is about changes in culture when different cultures are in contact—groups adopt and adapt traits from each other.

- Sanskritisation exactly fits this, as lower castes adopt upper-caste traits to change their social position.

The correct answer is Option 4: Acculturation.