Which statement describes a major advantage of a federal system of government over a unitary system
a. it ensures that a country's government cannot become authoritarian
b. it prevents a single nation government from holding all of a country's power
c. it eliminates a single national government in favor of individual state governments
d. it eliminates the possibility that individual states might pass conflicting laws

Option B.

Explanation:

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.

slavery, abortion, donald trump, gay marriage, racial rights, immigration  

explanation:

anything that has been broth up to the supreme court is something of grate political divide   so just look as court cases

a historian researching the immigration policies of the early 1900s would expect a source written today,rather than in 1910 to :

( a ) be more interested in objective data and statistics.