Correct answer: A. They organised Santhals against exploitation
Explanation: Direct answer: Option A, Sidhu and Kanhu organised the Santhals against exploitation. The Santhal Rebellion, also called the Santhal Hul, was an uprising in 1855–56 led prominently by Sidhu and Kanhu Murmu, along with other leaders. Santhal communities faced exploitation by moneylenders, revenue officials, zamindars and colonial authorities. Debt, unfair demands, loss of land and oppressive administration created intense anger. The leaders brought people together and challenged this system, so their importance was organisational and leadership-based. Option A is correct because it connects the named leaders with their community and the actual purpose of the rebellion. Option B is wrong because the Chipko Movement was a much later forest-protection movement, especially associated with Himalayan villagers and activists such as Gaura Devi and Sunderlal Bahuguna. Option C is wrong because Narmada Bachao Andolan was a later movement concerning dams and displacement. Option D is wrong because the Simon Commission was a British constitutional commission, not something formed by these Santhal leaders. Exam cue: match Sidhu and Kanhu with Santhal Hul, not with later environmental movements.