Answer : 3. "iron age"
Explanation :

1. All the houses of the Sunari civilization are built with the oldest iron ore melting furnaces.

2. Sunari civilization belongs to the Iron Age.

3. Sunari is a small village in Jhunjhunu district of Rajasthan.

4. It is situated near the Kantil river bank.

5. People of Sunari civilization mostly used rice and horses which is considered as Arya Vedic culture.