听力原文： People over the age of 65 in the U.S.A. are called senior citizens. Life for these people is different from that for younger Americans. Most senior citizens retire, or no longer work full time. Also it is unusual for people of this age to live with their children and grandchildren. Grandparents tend to live in their own houses or apartments away from their families. For many senior citizens, the year after 65 is not enjoyable. They feel unproductive when they no longer work. Their lives lose meaning. In addition, they may feel lonely being away from their families and the contacts they had in their work. Moreover, they become more concerned with their health as they grow olden If they live in big cities, they often worry about their safety. Other senior citizens enjoy their lives. They feel free to do things they were not able to do when they were working and raising families. They now have time to enjoy hobbies and sports and travel. They associate with their fellow senior citizens who have common interests and equal free time. Many senior citizens move to retirement communities located in warm climates. Some senior citizens continue to work beyond retirement age. Many find new careers and professional opportunities after they retire. The number of senior citizens in the U.S. is increasing rapidly because people are living longer than before. The average life span for Americans is now more than 74 years. Because of their larger numbers and more active life styles, senior citizens are gaining social influence in the country, both politically and economically. Their concerns are receiving a wider audience than ever before. The time may come when all Americans will look forward to becoming senior citizens. How old are senior citizens?