In which governmental system does power flow both ways between national and regional governments?

The correct answer is a federal system because, in this type of government, power is shared between national and regional governments. This dual system of governance allows both levels of government to operate independently in certain areas, while also collaborating in others.

In a federal system, the constitution often delineates the powers and responsibilities of each level of government, establishing a framework through which they can interact. This means that both the national government and the regional governments have the authority to legislate and regulate in specific domains, which promotes a system of checks and balances.

In contrast, a unitary system concentrates power at the national level, with regional governments operating under the authority of the central government, limiting their autonomy. A confederal system typically has a weak central authority where the regional governments hold most of the power and cooperate primarily through voluntary agreements. A presidential system pertains specifically to the executive structure of the government, where the president acts as the head of state and government, but it doesn't inherently relate to the flow of power between national and regional governments.