On which date was the drafting of the Constitution of India completed and formally adopted by the Constituent Assembly?

Introduction / Context:
The Constitution of India is the supreme law of the country, and its drafting and adoption are crucial milestones in Indian history. While the Constitution came into force on 26 January 1950, it was actually completed and formally adopted earlier. This question focuses on the exact date when the Constituent Assembly finished its work on the Constitution and adopted it.

Given Data / Assumptions:
- The question is about completion and formal adoption of the Constitution by the Constituent Assembly, not the date it came into force.
- Several key dates between 1948 and 1950 are listed as options.
- Only one date corresponds to the final adoption of the Constitution.

Concept / Approach:
The Constituent Assembly adopted the Constitution of India on 26 November 1949 after nearly three years of deliberations. The Constitution then came into force on 26 January 1950, chosen to honour the declaration of Purna Swaraj made on 26 January 1930. Understanding the distinction between adoption and enforcement is essential to answering this question correctly.

Step-by-Step Solution:
Step 1: Recall that the Constituent Assembly took about two years, eleven months, and eighteen days to draft the Constitution. Step 2: Remember that the Assembly finally adopted the Constitution on 26 November 1949. Step 3: Recognise that although adopted in November 1949, the Constitution came into effect later on 26 January 1950. Step 4: Review the options and identify 26 November 1949 as the date associated with completion and adoption. Step 5: Therefore select 26 November 1949 as the correct answer.

Verification / Alternative check:
Official records and standard polity references clearly state that 26 November 1949 is celebrated as Constitution Day to mark the adoption of the Constitution. The Preamble in original government publications carries this date as the date of adoption. This confirms the answer beyond doubt.

Why Other Options Are Wrong:
11 February 1948: A date during the drafting period but not associated with final adoption.
26 January 1950: This is the date when the Constitution came into effect and India became a republic, not the date of adoption by the Assembly.
None of these: Incorrect because there is a correct date listed among the options, namely 26 November 1949.
15 August 1949: Not a historically significant date related to adoption of the Constitution.

Common Pitfalls:
Many learners confuse adoption and enforcement and choose 26 January 1950 because it is better known as Republic Day. Another pitfall is to overlook 26 November 1949 because it is less frequently celebrated in everyday life, although it has been recognised officially as Constitution Day in recent years. To avoid errors, one should clearly remember both dates and their specific significance.

Final Answer:
The Constitution of India was completed and formally adopted by the Constituent Assembly on 26 November 1949.