阅读选择：阅读下面短文，请从短文后所给各题的四个选项(A、B、C、D)中选出一个最佳选项。

     Work is a very important part of life in the United States. Americans spend most of their lives working. For most Americans, their work defines them: They are what they do. What happens, then, when a person can no longer work?
     Most Americans stop working at the age of sixty-five or seventy and retire. Because work is such an important part of life in this culture, retirement can be very difficult. Retirees often feel that they are useless and unproductive. Of course, some people are happy to retire; but leaving one's job, whatever it is, is a difficult change, even for those who look forward to retiring. Retirement can also bring financial problems. Many people depend on Social Security checks every month. During their working years, employees contribute a certain percentage of their salaries to the government. Each employer also gives a certain percentage to the government. When people retire, they receive this money as income. These checks do not provide enough money to live on, however, because prices are increasing very rapidly. Senior citizens, those over sixty-five, have to have savings in the bank or other retirement plans to make ends meet. The rate of inflation (通货膨胀) is forcing prices higher each year; Social Security checks alone cannot cover these growing expenses. The government offers some assistance, but many senior citizens have to change their life-styles after retirement. They have to spend carefully to be sure that they can afford to buy food, fuel, and other necessities.
     Of course, many senior citizens are happy with their retirement. They have time to spend with their families or to enjoy their hobbies. Some continue to work part time; others do volunteer work. Some, like those in the Retired Business Executives Association, even help young people to get started in new business. Many retired citizens also belong to "Golden Age" groups. These organizations plan trips and social events. There are many other opportunities for retirees.