The correct answer is option 'D' - Nehru Report of 1928.

Explanation:

The idea of federation was first proposed in the Nehru Report of 1928. The Nehru Report was a significant document in the Indian nationalist movement that outlined the demands and aspirations of the Indian National Congress (INC) for self-governance and constitutional reforms in British India.

1. Nehru Report:
The Nehru Report was prepared by a committee of the All Parties Conference held in 1928 under the leadership of Motilal Nehru, the father of Jawaharlal Nehru. The report was a response to the Simon Commission, which had been appointed by the British government to recommend constitutional reforms in India.

2. Demand for Federation:
One of the key proposals of the Nehru Report was the demand for a federal structure for India. The report recommended the establishment of a federal government with autonomous provinces in order to accommodate the diverse regional and linguistic interests of the Indian population.

3. Features of Federation:
The Nehru Report outlined the features and principles of the proposed federation. It called for a federal government with a bicameral legislature, where the upper house would represent the provinces and the lower house would represent the people directly. The report also emphasized the importance of fundamental rights, responsible government, and separation of powers.

4. Provincial Autonomy:
The Nehru Report emphasized the need for provincial autonomy within the federal structure. It proposed that the provinces should have control over subjects like education, health, public works, and local government, while the federal government would be responsible for defense, foreign affairs, and communications.

5. Rejection and Impact:
Although the Nehru Report was a significant milestone in the Indian nationalist movement, it was ultimately rejected by the British government. However, the report played a crucial role in shaping the demands and aspirations of the Indian National Congress and provided a blueprint for future constitutional reforms in India.

Conclusion:
The Nehru Report of 1928 was the first proposal for a federal structure in India. It outlined the demands of the Indian National Congress for self-governance and constitutional reforms. While the report was not immediately accepted by the British government, it had a significant impact on the future course of the Indian nationalist movement and the eventual creation of an independent India.