Based on the report of Montagu-Chelmsford, the Government of India Act was enacted in 1919.

The correct answer is option 'C': the Government of India Act, 1919.

The Montagu-Chelmsford Report, also known as the Montagu-Chelmsford Reforms, was a significant milestone in India's constitutional development. It was a report prepared by the Secretary of State for India, Edwin Montagu, and the Viceroy of India, Lord Chelmsford, in 1918. The report proposed a series of constitutional reforms for India.

The report was a response to growing demands for greater participation of Indians in the governance of their country. It aimed to address the rising tide of nationalism and provide a framework for self-government in India. The report recognized the need for Indian involvement in policymaking and administration and recommended several important changes to the existing system.

The key features of the Montagu-Chelmsford Report are as follows:

1. Introduction of Dyarchy: The report proposed the introduction of a dual system of governance, known as dyarchy, at the provincial level. Under this system, certain subjects were to be transferred to Indian ministers, while others remained under the control of the Governor. This was a significant step towards self-government and increased Indian representation in the administration.

2. Expansion of Legislative Councils: The report recommended the expansion of legislative councils at both the central and provincial levels. The number of elected members in the councils was to be increased, allowing for greater representation of the Indian population.

3. Separation of Powers: The Montagu-Chelmsford Report emphasized the importance of separating the executive and legislative functions. It recommended that the executive functions be separated from the legislative functions, ensuring a more accountable and efficient government.

4. Introduction of Diarchy at the Center: The report suggested the introduction of a limited form of dyarchy at the central level, with certain subjects being devolved to Indian ministers. This would allow for the gradual transfer of power from the British government to Indian representatives.

The Government of India Act, 1919, also known as the Montagu-Chelmsford Reforms, was based on the recommendations of the Montagu-Chelmsford Report. The Act implemented many of the proposed reforms, including the introduction of dyarchy at the provincial level, the expansion of legislative councils, and the separation of powers. It marked a significant step towards self-government in India and laid the foundation for further constitutional reforms.

Hence, the Montagu-Chelmsford Report formed the basis for the Government of India Act, 1919.