a) They were Mahatma Gandhiji. and Dr. B.R. Ambedker.
b) The revolution referred here is repudiated (means deny) the caste system and to proclaim the oneness of the Hindu community.
c) Gandhiji brings the revolution by reminding the higher castes of their duty towards depressed. Babasaheb did the same by reminding the depressed, classes about their inherent rights to equality with the higher and powerful costes.