How things have changed! In 1995 the United States can look back on five years of solid growth while Japan has been struggling. Few Americans attribute this solely to such obvious causes as a devalued dollar or the turning of the business cycle. Self-doubt has yielded to blind pride." American industry has changed its structure, has gone on a diet, has learnt to be more quick-witted," according to Richard Cavanagh, executive dean of Harvard’s Kennedy School of Government," It makes me proud to be an American just to see how our businesses are improving their productivity, says Stephen Moore of the Cato Institute, a think-tank in Washington, DC. And William Sahlman of the Harvard Business School believes that people will look back on this period as" a golden age of business management in the United States."

　　51. The U.S.achieved its predominance after World War Ⅱbecause_____ .

　　[A] it had made painstaking efforts towards this goal

　　[B] its domestic market was eight times larger than before

　　[C] the war had destroyed the economies of most potential competitors

　　[D] the unparalleled size of its workforce had given an impetus to its economy

　　52.The loss of U.S. predominance in the world economy in the 1980s is manifested in the fact that the American_____.

　　[A] TV industry had withdrawn to its domestic market