The correct answer is: a) Central Assam (Nagaon area).
The Davaka Kingdom was an ancient kingdom located in the Nagaon area of central Assam. It was founded in the 6th century CE by the Chutiya dynasty. The kingdom reached its peak during the reign of King Bhaskarvarman in the 7th century CE. After his death, the kingdom declined and was eventually conquered by the Ahoms in the 13th century CE.
The Davaka Kingdom was a major power in ancient Assam. It controlled a large territory and had a strong military. The kingdom was also a center of learning and culture. The Davaka Kingdom was a significant part of the history of Assam.
Option b) Upper Assam is incorrect because the Davaka Kingdom was located in central Assam, not upper Assam.
Option c) Lower Assam is incorrect because the Davaka Kingdom was located in central Assam, not lower Assam.
Option d) Barak Valley is incorrect because the Davaka Kingdom was located in central Assam, not the Barak Valley.