单选题
This large city does almost no manufacturing and very little wholesale trade. Yet without the important service (1) provides, business everywhere would quickly grind to a (2) . Chaos would reign in all other leading cities. As you have guessed, the "product" we are talking about is government, and the city is the (3) of the United States, Washington, D. C. One out of every two persons (4) in the city works for the federal government. Washington has many (5) . It leads the nation in level of education achieved by its residents. More than fifteen percent of its adults have had four years or more of college. (6) scientists can be found here than in any other city. Since larger incomes are earned by (7) people, Washington has the highest median income of any city. Information is the vital force of the city. The Library of Congress (8) the largest and most comprehensive warehouse of information in the world. It contains 74 million items on hundreds of miles of (9) . In addition to books, these (10) include manuscripts, maps, photographs and documents. Papers of the Presidents all the way back to Washington are found here. The library is (11) to the public. It is considered by (12) to be one of the finest in the world. These people study the documents found in libraries. Washington has many important governmental buildings and historic shrines. (13) include the Capitol building, the White House, the Supreme Court, the Lincoln Memorial, and the Washington Monument. The Bureau of Engraving and Printing is (14) located here. This agency is responsible (15) putting new paper money into circulation. Tens of millions of dollars in money is (16) here every day. Unlike most cities, which grow in jumbled masses, Washington was planned on paper (17) any of its buildings were erected. The planners incorporated broad open areas around the historic landmarks and buildings. As a result the city is (18) . The central part of the city (19) a huge green park with broad, tree-lined boulevards and splendid (20) of its great structures.