Concept:
This question tests basic factual knowledge regarding the timeline of the Indian Constitution and its provisions on citizenship.
Step 1: Evaluating Assertion (A).
Assertion (A) is incorrect. The Constitution of India was adopted, enacted, and given to ourselves on November 26, 1949, not 1947. November 26 is now celebrated annually as "Constitution Day." In 1947, the Constituent Assembly was still in the early stages of drafting the document.
Step 2: Evaluating Reason (R).
Reason (R) is correct. Unlike federations like the USA, where individuals hold both state and national citizenship, India has Single Citizenship. Every person is a citizen of India only, regardless of the state in which they reside. This was designed to promote national unity and brotherhood.
Step 3: Conclusion.
Since Assertion (A) contains a factual error regarding the date (1947 vs 1949), the only appropriate choice is that (A) is incorrect while (R) is correct.