The correct answer is option 3 - Kashmir.

Rajtarangini is a historical chronicle written by Kalhan, an ancient Kashmiri author. It is known for providing a detailed account of the history of Kashmir, starting from ancient times to the 12th century. The name "Rajtarangini" translates to "The River of Kings," reflecting the book`s focus on the kings and rulers of Kashmir.

The chronicle covers various aspects of Kashmir`s history, including the political, social, and cultural developments of the region. It provides information about the different dynasties that ruled Kashmir, their achievements, conflicts, and interactions with neighboring kingdoms.

By studying Rajtarangini, historians gain insights into the political landscape, ruling dynasties, and societal changes that occurred in Kashmir over centuries. It is an important literary work that helps in understanding the rich history and heritage of the Kashmiri people.

In summary, Rajtarangini, authored by Kalhan, is a historical chronicle that describes the history of Kashmir.