Although the United States cherishes the tradition that it is a nation of small towns and wide open spaces, only one in every eight Americans now lives on a farm. The【B1】population trend has been a double one, toward both urbanization and suburbanization, Metropolitan areas have grown explosively in the past decade and nearly half this increase has been in the【B2】, With the rapid growth of cities has come【B3】rapid decentralization. The flight of Americans from the central city to the suburbs【B4】one of the greatest migrations of modern times; quiet residential sections outside cities have become conglomerations of streets, split-level houses, and shopping centers. 【B5】, this spurt of suburban expansion does not alter the basic fact that the United States【B6】one of the most urban nations on the face of the earth. Census Bureau【B7】show that the【B8】population has been shrinking steadily since 1880. When the United States became a nation it had no large cities at all; today【B9】fifty cities have populations of more than 258,000. Mammoth complexes of cities are developing in the area of the East Coast and the east north central states, on the pacific and Gulf coasts, and near the shores of the Great Lakes. Some sociologists now regard the entire 600-mile stretch between Boston and Washington, D.C.—an area holding a fifth of the country"s population—【B10】one vast city or, as they call it, megalopolis.

【正确答案】 B

【答案解析】解析：本题考的是对语篇上下文的理解，第一句中说到了"虽然美国珍惜其作为一个小镇与辽阔土地之国的传统，但如今只有1/8的美国人生活在农场里"，这表明现在的人口趋势才具有双重性，故选recent 。该空应填形容词，而nowadays为副词。

【正确答案】 D

【答案解析】解析：该空应填名词，故urban、rura两项中的形容词均不对；如果选cities ，则"大都市人口膨胀的1/2发生在城市里"，此外"大都市"与"城市"为一个概念，两者均包括市中心和郊区，故该项不符合逻辑。

【正确答案】 C

【答案解析】解析：第一段的后半段提到了城市郊区的迅速发展，而第二段的第一句"这种郊区的发展并不能改变这一基本事实，即美国已成为地球上最具城市化的国家之一"，上下文应为转折关系，B、D项都不对；词组"Despite of this"本身就不对，应为"Despite this"或"In spite of this"，故A项也不对。

【正确答案】 B

【答案解析】解析：根据上一句话的中心意思"这种郊区的发展并不能改变美国已成为地球上最具城市化的国家之一这一基本事实"可知"统计局的数字表明自1880以来人口数不断减少的地点不可能是城市，也不可能是郊区"，因为第一段中提到了郊区与城市发展的速度是一样的，故答案只能是B。