The correct answer is: a) Arunachal Pradesh.
The Balipara Frontier Tract and Sadiya Frontier Tract were British administrative divisions that encompassed parts of present-day Arunachal Pradesh. The Balipara Frontier Tract was created in 1873, and the Sadiya Frontier Tract was created in 1874. Both tracts were administered by the British government of India.
The Balipara Frontier Tract was located in the easternmost part of British India, bordering Assam and Burma. The Sadiya Frontier Tract was located to the south of the Balipara Frontier Tract, bordering Assam and Nagaland.
Both tracts were sparsely populated, and the majority of the population was made up of tribal peoples. The British government administered the tracts through a system of indirect rule, which meant that they allowed the tribal peoples to maintain their traditional way of life.
The Balipara Frontier Tract was abolished in 1951, and the Sadiya Frontier Tract was abolished in 1954. Both tracts were merged with Assam. In 1972, Arunachal Pradesh was carved out of Assam, and the Balipara Frontier Tract and Sadiya Frontier Tract became part of the new state.
The other options are incorrect because they do not encompass parts of present-day Arunachal Pradesh. Nagaland was a princely state under British rule, and Meghalaya and Mizoram were not created until after Indian independence.