Explanation:

- Federalism is a system of governance in which power is divided between a central authority and various constituent units.

- Option 1: Two - Federalism typically involves two levels of government: the central or national government and regional or state governments. This is the conventional structure seen in countries like the United States and India.

- Option 2: One - This is incorrect as federalism is about the division of power, inherently involving more than one level of government.

- Option 3: Four - This is rarely the case, as federal structures usually do not go beyond central and state/provincial levels.

- Option 4: Three - There are instances of three-tier federalism where administrative divisions add another layer, like local governments.

Option 1: Two is correct.

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