—Read the article below about the central problem of Economics. —Choose the best word to fill each gap, from A, B, C or D. —For each question 19-33,mark one letter (A, B, C or D) on your Answer Sheet. —There is an example at the beginning. The Central Problem of Economics The central problem of economics is to satisfy the people's and nation's wants. The problem we are faced with is that our resources, here identified as money, are limited. The only way we can resolve our problem is to make choices. After looking at our resources, we must examine our list of (19)______ and identify the things we need immediately, those we can postpone, and (20)______ we cannot afford. As individuals, we face the central problem involved in economics deciding just how to allocate (分配) our limited resources to provide (21)______ with the greatest satisfaction of our wants. Nations face the same problem. As a country's population grows the need for more goods and services grows correspondingly. Resources necessary to production may increase, but there (22)______ are enough re sources to satisfy the total desires of a nation. Whether the budget meeting is taking place in the family (23)______ room, in the conference room of the corporation (24)______ of directors, or in the chamber of the House of Representatives in Washington, the basic problem still exists. We need to find methods of allocating limited resources in order to satisfy unlimited wants. A short time ago economists (25)______ goods into two categories, free and economic. The former, like air and water, were in (26)______ abundance that economists had no concern for them. After all, economics is the (27)______ of scarcity (匮乏) and what to do about it. Today many of these 'free goods' are (28)______ very expensive to use. Pollution has made clean air and water expensive for producers who have to filter their waste products, for consumers who ultimately (最终) (29)______ the producers' extra costs, and (30)______ taxpayers who pay for the government's involvement in cleaning the environment. In the 1990s, almost all goods are (31)______ Only by effort and money can they be obtained in the form. people wish. Meeting the needs of people and forming resources available (32)______ the basic activity of production. In trying to meet (33)______ wants from limited economic goods, production leads to new problems in economics.