The correct options are
C 26 November 1949 - Assembly adopts constitution
D 26 January 1950 - Constitution came into effect
The Constituent Assembly spent 114 days spread over three years to consider the Draft Constitution. It finally adopted the Constitution on 26 November 1949; it came into effect on 26 January 1950. To recognise this, 26 January of every year is celebrated as India's Republic Day.