Answer:
A(n) referendum is an amendment that is presented to the people on the ballot of a statewide election to vote on.
Step-by-step explanation:
Initiative: "the right of citizens outside the legislature to originate legislation"
Referendum: "a general vote by the electorate on a single political question which has been referred to them for a direct decision"
Federalist system: "the constitutional division of power between U.S. state governments and the federal government of the United States"
Supremacy clause: "prohibits states from interfering with the federal government's exercise of its constitutional powers"
So, the best answer choice is B.