Option 4 is correct, i.e. The Government of India Act 1919.
In 1918, Edwin Montagu, the Secretary of State, and Lord Chelmsford, the Viceroy, produced their scheme of constitutional reforms which led to the enactment of the Government of India Act of 1919.
The Provincial Legislative Councils were enlarged and the majority of their members were to be elected.
The provincial governments were given more powers under the system of Dyarchy.
Under this system, the various subjects of the government were divided under reserved and transferred.