Explanation:

Jyotiba Phule, a pioneering social reformer and anti-caste activist from Maharashtra, authored the influential book 'Gulamgiri' (Slavery) in 1873. This work served as a powerful critique of the caste system and Brahminical dominance, drawing parallels between the subjugation of lower castes in India and the institution of slavery in America. Ishwar Chandra Vidyasagar was known for educational and social reforms, particularly for women. Acharya Vinoba Bhave was a spiritual leader and proponent of the Bhoodan Movement. Dadu Dayal was a 16th-century saint, not associated with this book.