Which statement best summarizes the relationship between the federal government and state governments?

a.
state constitutions grant the states absolute authority over their lands but reserve certain powers for the federal government.

b.
the federal government sets tax policy within the states, but the states determine how tax money is spent.

c.
state governments must obey the federal government's orders unless they violate their state constitutions.

d.
the constitution reserves certain powers for the states, but states must share other powers with the federal government.