The correct answer is option 4, B.R. Ambedkar. B.R. Ambedkar, also known as Babasaheb Ambedkar, founded the `All India Depressed Classes Federation` in 1920. He was a prominent leader and social reformer who dedicated his life to fighting for the rights and upliftment of the marginalized communities in India, especially the untouchables or Dalits. Ambedkar played a crucial role in the drafting of the Indian Constitution and is often referred to as the architect of the Indian Constitution. He also advocated for equal rights and opportunities for women and believed in the principle of social justice. Ambedkar`s efforts and contributions continue to inspire and shape the social and political landscape of India.