The federal system of government is exemplified in the United States, hence option A is correct. The other practice is the parliamentary system.
See the explanation below.
Simply put, a federal system or a federated system is one in which the powers of government are split at the national level, state level, and local government level.
It is mostly believed that in the federal system of government, the government is brought closer to the people by the way of the split in power.
Learn more about the federal system here:
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