The structural part of the Indian Constitution is largely derived from the:

The Constitution of India drew on many sources, both Indian and foreign. The single largest source was the Government of India Act, 1935, passed by the British Parliament. About 250 provisions of the Constitution were taken from it, either word for word or with small changes. The structural part of the Constitution, which sets up the framework of government and the relationship between its organs, is largely based on this Act.

Features borrowed from the Government of India Act, 1935 include:

• The federal scheme, with a division of powers between the Centre and the provinces.
• The three lists of subjects (Federal, Provincial and Concurrent), which became the Union, State and Concurrent Lists.
• The office of Governor.
• The judiciary, including the Federal Court, which became the Supreme Court.
• Public Service Commissions.
• Emergency provisions.
• Administrative details.
• As the political scholar Granville Austin and others have noted, the Constituent Assembly chose to build on familiar institutions to ensure continuity and stability.

The philosophical part of the Constitution (the Fundamental Rights and the Directive Principles) came mainly from the American and Irish Constitutions. The political part (the principle of cabinet government and the relations between the executive and the legislature) came largely from the British Constitution.

The Government of India Act, 1935 was itself the longest Act passed by the British Parliament for India. It provided for provincial autonomy, which came into force in 1937, and for an All-India Federation, which never came into being.

Why not the other options?

• ✗The Indian Councils Act, 1909 (Morley-Minto Reforms) introduced separate electorates for Muslims.
• ✗The Government of India Act, 1919 (Montagu-Chelmsford Reforms) introduced dyarchy in the provinces.
• ✗The Indian Independence Act, 1947 ended British rule and created two dominions, India and Pakistan.