The correct answer is D. Ambedkar.
Gulamgiri (Slavery) is a book written by B. R. Ambedkar, an Indian jurist, economist, politician and social reformer who campaigned against social discrimination against Dalits, women and labourers. The book was first published in 1927 and is considered to be one of the most important works on caste discrimination in India.
Sir Syed Ahmed Khan was a Muslim reformer and educationist who founded the Aligarh Muslim University. He is considered to be one of the founders of modern India.
Rammohan Roy was a Bengali polymath who is considered to be the father of modern Indian Renaissance. He was a social reformer, writer, philosopher, and the founder of the Brahmo Samaj.
Jyotiba Phule was a social reformer and thinker who is considered to be the father of the Indian social reform movement. He was a pioneer in the fight against caste discrimination and women’s rights.