The correct answer is option 2: Federal government. Dual citizenship refers to the status of an individual who is a citizen of two different countries. In a federal government system, power is divided between a central government and multiple regional governments or states. Each state has its own set of laws and regulations, including citizenship laws. This means that an individual may hold citizenship in both the central government and one of the regional governments. In contrast, in a unitary government system, power is concentrated in a single central government, which makes it less likely for dual citizenship to be recognized. Similarly, in parliamentary and presidential government systems, citizenship laws are typically determined by the central government, making dual citizenship less common.