Federalism and the 10th amendment work together--the 10th Amendment states that if something is not covered by the Constitution and there is no specific federal power, then the power goes to the state.
Federalism is the principle that government should be divided between a central power and regional powers. In the case of the 10th Amendment, if the central power doesn't have explicit power to do something then the states have the power to do so.
A.
Pearl Harbor attack setitoff
A. German had to pay costly war reparations. “Not sure”
