Explanation

When the Constitution of India came into full force on 26th January 1950, the original Preamble drafted by the Constituent Assembly declared India to be a:

– ’SOVEREIGN DEMOCRATIC REPUBLIC’.
– The words ’SOCIALIST’ and ’SECULAR’ (along with the phrase ‘and integrity’) were subsequently inserted into the Preamble by the 42nd Constitutional Amendment Act of 1976 during the Emergency.

Consequently, on 26th January 1950, the exact constitutional status was a Sovereign Democratic Republic — Option B.