Why is the amendment process in the Constitution an example of federalism?

A: It takes place at the federal level with input from Americans willing to travel to the nation's capital.

B: It takes place at the state level, but federal officials from each branch of government have to approve it.

C: It specifies that each amendment must be ratified first by the states and then proposed by Congress.

D: It requires cooperation between the state and national governments to ratify an amendment.