The correct answer is option 4: 26th November 1949. The Constitution of India was not adopted on 26th January 1950, as mentioned in option 1. However, 26th January 1950 holds significance as it is the date when the Constitution came into effect and India became a republic.

Option 2: 15th August 1947 is incorrect. This date marks India`s independence from British rule and the beginning of the Dominion of India, but it is not the date when the Constitution was adopted.

Option 3: 30th January 1948 is incorrect. This date is significant as it marks the assassination of Mahatma Gandhi, but it is not the date of the adoption of the Constitution.

Unlike the other options, option 4 correctly states that the Constitution of India was adopted by the Constituent Assembly on 26th November 1949. This means that the Constituent Assembly finalized and approved the Constitution on this date. It was later ratified and came into effect on 26th January 1950, when India officially became a republic.