The correct answer is: B. Chhota Nagpur.
The Santhal Revolt was a major tribal revolt against the British East India Company in 1855. The revolt was led by Sidhu and Kanhu Murmu, two Santhal brothers. The rebels were motivated by a number of factors, including British encroachment on Santhal land, high taxes, and forced labor. The revolt was initially successful, but it was eventually suppressed by the British.
The British were supported by the ruler of Chhota Nagpur, Raja Raghunath Sahi. Raja Sahi was a Hindu Rajput who had been appointed by the British to rule over Chhota Nagpur. He was loyal to the British and helped them to suppress the Santhal Revolt.
The other options are incorrect. The Chero ruler was not supportive of the British during the Santhal Revolt. The Manbhum ruler was also not supportive of the British. The Ramgarh ruler was initially supportive of the British, but he later switched sides and supported the Santhal rebels.
The Santhal Revolt was a significant event in the history of Jharkhand. It was a major uprising against British rule and it led to a number of changes in the way that the British governed the region. The revolt also had a lasting impact on the Santhal people, who continue to commemorate it today.