Justice O'Connor's dissent in Raich pointed out that one of federalism's chief virtues is what?
a. The federal government is never permitted to regulate in an area where the states are permitted to regulate
b. States are never permitted to regulate in an area where the federal government also regulates
c. States can choose different ways to regulate in efforts to solve problems, without requiring all states to adopt the same solution
d. It rests primary power in the federal government to regulate significant issues impacting the nation