Answer : 2. "Treaty of Prague"
Explanation :

The Treaty of Prague was signed on August 23, 1866, between Austria and the Kingdom of Italy. As a result of this treaty, Austria agreed to cede the territory of Venetia to Italy. This territorial transfer was part of the broader context of the Austro-Prussian War of 1866, also known as the Seven Weeks' War, where Austria faced defeat against Prussia. The treaty contributed to the process of Italian unification, as Venetia was an important region that was integrated into the newly formed Kingdom of Italy.