It prevents a single nation government from holding all of a country's power, is the correct answer.
A federal system of government is a form of government in which the government shares its power between the federal (national) and the state and provincial government. Under this form of government, every level of government has autonomy in some fields and shares powers in other fields. Therefore, the advantage of the federal government can be seen in the fact that it prevents a single national authority from containing all of a country's power.
