'A' was a leader of the Dalits and the law minister of the Government of India from 1947 to 1951. He took a leading part in the framing of the Indian constitution, outlawing discrimination against untouchables, and skillfully helped to steer it through the assembly. In October 1956, in despair because of the continuation of untouchability in Hindu doctrine, he renounced Hinduism and became a Buddhist, together with about 200,000 fellow Dalits, at a ceremony in Nagpur. Identify 'A'.