Answer:
one prohibited midterm pay raises for members of Congress
Explanation:
Twelve constitutional amendments passed Congress in the earliest days of the Republic, ten of which became the Bill of Rights, one involving apportionment of the House of Representatives that was never ratified and one prohibited midterm pay raises for members of Congress that eventually became the Twenty-Seventh Amendment.
The Congressional Apportionment Amendment is the only one of the twelve amendments passed by Congress which was never ratified