In the 19th century under Chief Justice Taney, federalism became understood as dual federalism. The idea of dual federalism is

a. that both state and national governments have the same power, like the power to tax.
b. that the national government's area of power is in the areas of national defense, foreign policy, and interstate commerce, while states are responsible for everything else.
c. that a government policy is funded by one level of government but carried out by a different level of government.
d. that one level of government works to check another level of government to prevent it from becoming too powerful.

b