The correct answer is option 4, B.R. Ambedkar. B.R. Ambedkar was a prominent social reformer and leader of the Dalit community in colonial India. He played a significant role in advocating for the rights and upliftment of the Dalits (also known as the Depressed Classes). Ambedkar founded the “All India Depressed Classes Association” in 1930, which later came to be known as the “Scheduled Castes Federation.” This organization aimed to fight against the discrimination and social injustices faced by the Dalits and worked towards their political and social empowerment. Ambedkar`s efforts were instrumental in the inclusion of provisions for the welfare and upliftment of the Scheduled Castes in the Indian Constitution. His work had a profound impact on the lives of marginalized communities in India.