Which of the following is the part of the ratification process in the U.S. Constitution that has never been used?

(1 point)
• Congress calls for a national constitutional convention
• Congress votes by two-thirds majority vote to propose an amendment
O three-fourths of state conventions ratify an amendment
• three-fourths of state legislatures ratify an amendment

The part of the ratification process in the U.S. Constitution that has never been used is: Congress calls for a national constitutional convention.