Who established Arya Samaj?

c) is correct. Swami Dayanand Saraswati established the Arya Samaj in 1875

a) is incorrect. Raja Rammohun Roy spearheaded the creation of Brahma Samaj

b) is incorrect. Keshab Chandra Sen was the successor of Rammohun Roy at Brahma Samaj

d) is incorrect. Debendranath Tagore was the successor of Rammohun Roy at Brahma Samaj