Explanation:

The GOI Act of 1919 provided a dual form of government (a "diarchy") for the major provinces. In each such province, control of some areas of government, the "transferred list", were given to a Government of ministers answerable to the Provincial Council. The 'transferred list' included agriculture, supervision of local government, health, and education. The Provincial Councils were enlarged.
At the same time, all other areas of government (the 'reserved list') remained under the control of the Viceroy. The 'reserved list' included defence (the military), foreign affairs, and communications.
It relaxed the central control over the provinces by demarcating and separating the central and provincial subjects. The central and provincial legislatures were authorised to make laws on their respective list of subjects. However, the structure of government continued to be centralised and unitary.