Passage ThreeQuestions 31 to 35 are based on the following passage.Many people have come up with ideas to ease some of the problems associated with population growth. For example, paper manufacturing companies in the United States do business with the logging(伐木) industry, which cuts down the trees needed to make paper. In recent years, most paper companies have realized that the cutting down of trees Can do a great deal of harm to the environment. Therefore, these paper companies now provide money for programs for planting new trees to replace those that have been cut down.Similarly, most communities in the United States have a recycling program. These programs recycle newspapers, glass bottles, and tin Cans. The recycling of newspapers means that new paper can be made from old paper instead of from fresh wood. Many city and other local govemments in the United States make certain that at least some of the paper they purchase comes from recycling, rather than from cutting fresh timber.In some parts of the United States, few businesses have been moving to small cities instead of large ones. This idea cuts down on problems such as overcrowding that are caused by the numbers of people in the largest cities.Developing smaller cities-called "micropolitan" areas--have certain advantages. Because these cities are closer to rural areas. They can help sustain and even revive rural economies through small-scale industries, including the processing and marketing of agricultural products. In addition, the governments of micropolitan areas can respond more quickly and effectively to the needs of their residents, especially the poor.It is easy to become discouraged by the environmental damage and other problems that rapid population growth causes. Some of that damage cannot be completely undone. Many scientists, however, are confident that by carrying out ideas such as these, in addition to better conserving the resources we have not yet used, we can reduce the negative impact on our lives.
31.Most paper manufacturing companies in the US now________.