Concept:The Arya Samaj was a Hindu reform movement, and Swami Dayanand Saraswati founded it.Explanation:He established the Arya Samaj in 1875 at Bombay.His movement opposed idol worship and supported Vedic principles.Among the other options, Swami Vivekanand founded the Ramakrishna Mission in 1897.Raja Ram Mohan Roy founded the Atmiya Sabha in 1815.Thus, the correct founder of the Arya Samaj is Swami Dayanand Saraswati.Answer:Option A: Swami Dayanand Saraswati.