The answer to the question is option 'C' - 26 January 1950.

Explanation:
The Constitution of India is the supreme law of the country. It lays down the framework that defines the political principles, establishes the structure, procedures, powers, and duties of the government institutions, and sets out the fundamental rights, directive principles, and the duties of citizens. The Constitution of India came into effect on 26 January 1950.

The process of drafting and adopting the Constitution of India began soon after India gained independence from British colonial rule on 15 August 1947. A Constituent Assembly was formed to draft the Constitution. The members of the Constituent Assembly were elected by the provincial assemblies, with each province and princely state having proportional representation.

The drafting process of the Constitution took around three years, during which the Constituent Assembly deliberated on various issues and debated the provisions. The Constituent Assembly had several committees, including the Drafting Committee headed by Dr. B.R. Ambedkar, which played a crucial role in formulating the final draft of the Constitution.

After extensive discussions and amendments, the final draft of the Constitution was adopted by the Constituent Assembly on 26 November 1949. However, the Constitution did not come into effect immediately after adoption. It was decided that the Constitution would be implemented on 26 January 1950, to coincide with the anniversary of the Purna Swaraj (Complete Independence) declaration made by the Indian National Congress in 1930.

On 26 January 1950, the Constitution of India was formally enacted, and India transitioned from a dominion to a republic. This day is celebrated as Republic Day in India, marking the adoption of the Constitution and the establishment of the democratic system of governance.

In conclusion, the Constitution of India came into effect on 26 January 1950, after being adopted by the Constituent Assembly on 26 November 1949. This date was chosen to commemorate the historic moment of India becoming a republic.