Answer : 3. "Maratha invasion"
Explanation :

1. It was held in the year 1734 and was presided over by Jai Singh and other prominent rulers of different regions of Rajasthan.

2. The objective of the meeting was to unite the forces of various Rajput tribes and to observe and check the increasing invasions of foreigners on their lands.

3. During that period, the Marathas also started invading lands and were gaining prominence.

4. Rajput leaders soon realized that Mughal power was unable to resist Maratha expansion and decided to hold a conference at Hurda to discuss the terms of a united Rajputana front against the Marathas.

5. After prolonged deliberations, an agreement was signed on 17 July 1734.