The correct answer is option 2, Keshub Chandra Sen. The Indian Reform Association was founded by Keshub Chandra Sen in 1870. It was a social and religious reform movement that aimed to bring about progressive changes in Indian society. Keshub Chandra Sen was a prominent figure in the Brahmo Samaj, a socio-religious reform movement.

Option 1, Debendranath Tagore, was the father of Rabindranath Tagore and an important figure in the Brahmo Samaj movement, but he was not the founder of the Indian Reform Association.

Option 3, Rammohan Roy, was a pioneer of social and religious reform in India, but he lived in the 19th century much before the establishment of the Indian Reform Association.

Option 4, Dayanand Saraswati, was the founder of the Arya Samaj, another influential reform movement, but he was not associated with the Indian Reform Association.