Which statement is true about many of the amendments added to the U. S. Constitution after the Bill of Rights? They were written before the Civil War. They changed the structure of the federal government. They extended rights of citizenship to new groups. They made it harder for some people to vote.

I would say the one that is most right, is, "They extended the rights of citizenship to new groups."

Explanation:

Most of the amendments, from the 13th amendment to the 27th amendment were passed after the civil war, so that is incorrect.

The amendments also made it much easier for many groups of people to vote. In fact, many of the amendments center around allowing groups of people to vote, and have citizenship.

Which leads me to the answer which I believe is correct, which is, "They extended the rights of citizenship to new groups."