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

The Montagu-Chelmsford Report, also known as the Montagu-Chelmsford Reforms, was a significant document in the history of India's constitutional development. It was prepared by the Secretary of State for India, Edwin Montagu, and the Viceroy of India, Lord Chelmsford, in 1918. The report recommended several reforms to the constitutional structure of British India.

The Montagu-Chelmsford Report led to the enactment of the Government of India Act, 1919. Let's understand the details of this act and how it was influenced by the report:

1. Background:
- The British government recognized the need for reforms in India after the First World War to address growing Indian nationalist aspirations.
- Edwin Montagu, the Secretary of State for India, was sympathetic towards Indian demands for self-government and was appointed to formulate a scheme of reform.

2. Recommendations of the Montagu-Chelmsford Report:
- The report recommended the gradual introduction of responsible government in India.
- It proposed the establishment of a dual system of governance, with a centralized government at the center and provincial governments in the provinces.
- It recommended the expansion of legislative councils and the inclusion of elected Indian representatives.
- It suggested the separation of provincial executive functions from legislative functions, allowing elected members to have a say in policy matters.
- It proposed the introduction of dyarchy, a system where certain subjects would be transferred to Indian ministers, while others would remain under the control of British officials.

3. Government of India Act, 1919:
- The Government of India Act, 1919, was based on the recommendations of the Montagu-Chelmsford Report.
- It introduced several important reforms, including the expansion of legislative councils and the inclusion of elected Indian representatives.
- It established a dual system of governance, with separate functions for the central and provincial governments.
- It introduced the concept of dyarchy in the provinces, dividing executive functions between elected Indian ministers and British officials.
- It provided for the appointment of a Public Service Commission to ensure the recruitment of civil servants on the basis of merit.

In conclusion, the Government of India Act, 1919, was based on the Montagu-Chelmsford Report. This act introduced significant reforms in the constitutional structure of British India, aiming to gradually increase Indian participation in governance and move towards self-government.