The correct answer is: A. Swami Sahajanad.
Swami Sahajanad was a Hindu religious leader who preached against the exploitation of the Munda people by the British and the Hindu landlords. He was a charismatic figure who attracted a large following among the Munda people. He is credited with inspiring Birsa Munda to lead the Munda rebellion against the British.
Anand Pandey was a freedom fighter who was involved in the Indian independence movement. He was not a mentor of Birsa Munda.
Jatra Bhagat was a Munda religious leader who preached against the exploitation of the Munda people by the British and the Hindu landlords. He was a contemporary of Swami Sahajanad, but he was not his mentor.
M. N. Roy was a revolutionary who was involved in the Indian independence movement. He was not a mentor of Birsa Munda.