The correct answer is Option 3- Ishwar Chandra Vidyasagar

Ishwar Chandra Vidyasagar was a Bengali polymath, a social reformer, and a key figure of the Bengal Renaissance. He is best known for his campaign to allow Hindu widows to remarry. Vidyasagar used ancient Hindu texts to argue that widow remarriage was not prohibited. He cited the Manusmriti, which states that a widow may be remarried if her husband dies childless. He also cited the Mahabharata, which tells the story of Draupadi, who was married to five men.

Vidyasagar's campaign was successful, and the Hindu Widows Remarriage Act was passed in 1856. This act allowed Hindu widows to remarry, and it was a major step forward for women's rights in India.

The other options are incorrect. Narayan Guru was a social reformer from Kerala, India. He did not campaign for widow remarriage. Pandita Ramabai was an Indian social reformer and educationist. She did not campaign for widow remarriage, but she did work to improve the lives of widows. Raja Ram Mohan Roy was a Bengali polymath and social reformer. He was a pioneer of the Brahmo Samaj, a reform movement that advocated for gender equality. He did not campaign for widow remarriage, but he did work to improve the lives of women in general.