Concept:Power sharing between central and regional governments is the key feature of federalism.
Explanation:In a federal structure, the central government and the state or regional units each have their own defined powers.
This constitutional division of authority prevents the centre from dominating the units.
The word "federalism" correctly describes this arrangement because it involves a formal sharing of power between the centre and the constituent units.
Other options do not fit: confederal means a loose union of independent states, unitary means power is concentrated in the centre, and oligarchic refers to rule by a small group.
Answer:The correct option is D. federalism.