A、To lock people. B、To punish people. C、To sentence people. D、To isolate people. A短文开始部分提到，很久以前，监狱只是用来关押待惩罚的人的。

In the history of human civilization, the use of prisons as punishment for crimes is of recent origin.(22)A long time ago, prisons were merely places to lock persons. People were locked up in them to wait for the punishment.(23)In the late Middle Ages, the people of Europe became angry about the cruelties of that system and protested. Therefore, less cruel punishments were used. For example, people were sent away from their country and were never allowed to come back, or they were kept in prison. The early settlers of America brought with them the idea of isolating prisoners. They could not see or talk to each other and could only read and exercise by themselves. After a long isolation, the prisoners could be released because they would not commit any more crimes. The Walnu Street Jail in America operated on this idea. In the latter part of the 18th century, however, a religious group stopped that system.(24)At the end of the 19th century, a new idea was introduced; It permitted prisoners to work together in groups during the day. It also reduced problems of administration. Afterwards, many prisons were built in America and abroad, which operated on this idea.(25)About the time of the American Civil War, a new institution for young offenders was built in Elmira, New York. This new system worked on the principles of classifying prisoners on the basis of age, giving them an education and training them.
22. What was the initial use of prisons?
23. Why were less cruel punishments used in the late Middle Ages?
24. What was the new idea to treat prisoners at the end of the 19th century?
25. What can we learn about the new prison system during the American Civil War?