The correct answer is: a) Raja.
A Raja is a Hindu title for a king or prince. It is derived from the Sanskrit word “raja” meaning “king”. The title was used in India and Southeast Asia to refer to rulers of various ranks, from petty chieftains to powerful emperors.
In the context of the question, the rulers of feudatory states were often titled Raja. Feudatory states were those that were subordinate to a larger kingdom or empire. The Rajas of these states were often vassals of the larger ruler, and were required to pay tribute and provide military support.
The other options are incorrect. Gohain is a title used for a high-ranking official in the Ahom kingdom of Assam. Phukan is a title used for a military commander in the Ahom kingdom. Borua is a generic term for Assamese people.
I hope this helps!