Correct Option
On 26th January 1950, the constitutional status of India, as outlined in the Preamble to the Constitution, was a 'Sovereign Democratic Republic'. The original Preamble did not include the terms 'Socialist' and 'Secular'. These words were subsequently added to the Preamble by the 42nd Constitutional Amendment Act of 1976.
Incorrect Options
Option (a) is incorrect because while India was a Democratic Republic, the term 'Sovereign' was also an integral part of its constitutional status as per the Preamble on that date.
Option (c) is incorrect because the word 'Secular' was not present in the original Preamble of 1950. It was incorporated later by the 42nd Constitutional Amendment Act, 1976.
Option (d) is incorrect because both 'Socialist' and 'Secular' were added to the Preamble by the 42nd Constitutional Amendment Act, 1976, and therefore were not part of India's constitutional status on 26th January 1950.