Explanation:

With the Forty-second Amendment of the Constitution of India enacted in 1976, the Preamble to the Constitution asserted that India is a secular nation. In practice, unlike Western notions of secularism, India's secularism does not separate religion and state. A secular state is an idea pertaining to secularity, whereby a state is or purports to be officially neutral in matters of religion, supporting neither religion nor irreligion. Hence all option 4th is correct.