The correct option is D He was against child marriage.
Swami Dayanand Saraswati promoted monotheism, condemned idolatry and rejected the Brahmin domination of ritual and social practices. He was against child marriage, the prohibition of widow remarriage and how foreign travel had a polluting effect on our culture. He also spoke against the conversion of people from Hinduism to Christianity and Islam. For this he started counter-conversion, a process called Suddhi, directed at Hindus who had converted to other religions.