Explanation:

The Constitution of India came into force on 26 January 1950. The Constitution Assembly set up a Drafting Committee under the Chairmanship of Dr. B. R. Ambedkar on 29 August, 1947 to prepare a Draft Constitution for India. The Constitution of India was adopted by the Constituent Assembly on 26 November 1949 and came into force on 26 January 1950. (The process took 2 years, 11 months and 18 days - at a total expenditure of Rs 6.4 million to finish). Hence option 1st is correct.