The correct answer is option 3, which is the Government of India Act, 1935. Provincial autonomy refers to the decentralization of power and granting of self-governance to the provinces or states within a country.

Option 1, the Morley-Minto Reforms, introduced in 1909, aimed to provide limited representation to Indians in the legislative bodies, but it did not grant provincial autonomy.

Option 2, the Montagu-Chelmsford Reforms, implemented in 1919, introduced some degree of self-governance, but it did not establish complete provincial autonomy.

Option 4, the Indian Independence Act, 1947, is related to the partition of India and the creation of Pakistan, marking the end of British colonial rule. However, it did not introduce provincial autonomy.

The Government of India Act, 1935, was a significant constitutional reform that granted significant autonomy to provinces in India. It allowed for the establishment of provincial legislatures with the power to make laws on several subjects, including health, education, and agriculture. This act laid the groundwork for the establishment of a federal system in India.