Why Have U.S.states Been Called Laboratories of Democracy

Multiple Choice

Why have U.S.states been called laboratories of democracy?

A) They demonstrate the ideal structure of democracy in a unitary state.
B) They are forced to alter national policies that they disagree with.
C) Democracy is practiced at the state level but not at the national level.
D) States can experiment with new programs,which,if successful,can be copied nationwide.