The correct option is A 42nd Amendment of the Constitution
Option A is the correct answer. The word 'socialist secular' and 'unity and integrity of the Nation' were added to our Constitution by 42nd Amendment of the Constitution. The 42nd amendment to Constitution of India, officially known as The Constitution (Forty-second amendment) Act, 1976, was enacted during the Emergency (25 June 1975 – 21 March 1977) by the Indian National Congress government headed by Indira Gandhi.