The correct answer is: b) Promoting education in Arunachal Pradesh.
Tomo Riba was the first Chief Minister of Arunachal Pradesh. He was a visionary leader who played a key role in the development of the state. He was also a strong advocate for education and worked tirelessly to improve the educational opportunities for the people of Arunachal Pradesh.
Option a) is incorrect because Tomo Riba was not involved in the Indian freedom struggle. He was born in 1923, after India had already gained independence.
Option c) is incorrect because Tomo Riba was not a tribal rights advocate. He was a member of the Adi tribe, but he did not focus on tribal rights advocacy.
Option d) is incorrect because Tomo Riba was not involved in conservation efforts. He was a politician and a social worker, but he did not focus on conservation.
Tomo Riba was a great leader who made a significant contribution to the development of Arunachal Pradesh. He is remembered for his role in promoting education in the state.