Explanation:

- Zamindari system

- This was a land revenue system where landlords (zamindars) collected taxes from peasants.

- It was not related to caste-based service exchange.

- Tinkathia system

- A system practiced in Bihar, where peasants were forced to grow indigo on part of their land.

- It had no connection with caste services.

- Varna system

- This refers to the broad fourfold division of society (Brahmin, Kshatriya, Vaishya, Shudra).

- It is about social stratification, not specific service exchange.

- Jajmani system

- This was the traditional system where specific castes provided services (like priests, potters, barbers, etc.) to others in the community.

- It was a network of hereditary service relationships among castes.

Correct answer:

Option 4, Jajmani system