资料： The poverty line is the minimum income that people need for an acceptable standard of living. People with incomes below the poverty line are considered poor. Economists study the causes of poverty in order to find solutions to the problem. As the general standard of living in the country rises, the poverty line does, too. Therefore, even with today’s relatively high standard of living, about 10 percent of the people in the United States are below the poverty line. However, if these people had stable jobs, they could have an acceptable standard of living. Economists suggest several reasons why poor people do not have jobs. For one thing, more than half of the poor people in the United States are not qualified to work. Over 40 percent of the poor. People are children. By law, children less than 16 years old cannot work in many industries. A large number of poor people are Old. Many companies do not hire people over 65 years old, the normal retirement age. Some poor adults do not look for jobs for a variety of personal reasons: they are sick, they do not have any motivation, they have family problems, or they do not believe that they can find a job. Other poor people look for a job but cannot find one. Many poor adults never went to high school. Therefore, when they look for jobs, they have few skills that they can offer. At the present time, the government thinks it can reduce poverty in the country in the following ways. First, if the national economy grows, businesses and industries hire more workers. Some of the poor who are qualified to look for jobs may find employment. Then they will no longer be below the poverty line. Second, if society invests in the poor, the poor will become more productive. If the government spends money on social programs, education, and training for poor people, the poor will have the skills to offer. Then it is more likely that they can find jobs. Finally, if the government distributes society"s income differently, it raises some poor people above the poverty line. The government collects taxes from the non－poor and gives money to the poor. These payments to the poor are called welfare. In 1975 over 18 million people in the United States received welfare. Some economists are looking for better solutions to the poverty problem. However, at the present time, many people depend on welfare for a minimally acceptable standard of living. According to the passage, which of the following is NOT the reason of unemployment?