Concept:A unitary system is one in which the central government holds supreme power over all other levels of government.
Explanation:In a unitary system, regional or local governments exist only at the centre's discretion.
They exercise only the powers that the central government delegates to them.
This arrangement makes the central government supreme over every other level.
In a federal system, power is constitutionally shared between the central and regional governments.
In a confederal system, the regional governments are supreme, not the centre.
A totalitarian system describes absolute control by a ruler or party, not the hierarchy of government levels.
Since the question describes the central government as being supreme over other levels, the correct system is the unitary one.
Answer:D. unitary