A、1,000 B、23,000 C、20,000 D、2,000 DA、B、D三个选项都在原文中出现过，其中A是1968年的餐厅数量，B是日前的餐厅总数量， D才是正确答案。

Americans now spend more money on fast food than they do on higher education, personal computers, software or new cars. The rapid growth of the fast-food industry has been driven by fundamental changes in the U.S. economy. The hourly wage of the average American worker peaked in 1973 and then steadily declined until last year. Women entered the work force in record numbers, often motivated less by feminism than by a need to help pay the bills. In 1975, about a third of American mothers with young children worked outside the home; today about two-thirds of such mothers are employed. As the sociologists Cameron Lynne Macdonald and Carmen Sirianni have noted, the entry of women into the nation’s work force has greatly increased demand for the types of services that housewives traditionally performed: cooking, cleaning and child-care. The fast-food industry has benefited from these demographic changes, supplying at low cost the meals no longer prepared in the home and hiring at low wages millions of young women in need of extra income.
    The McDonald’s Corp. has become a powerful symbol of America’s service economy, the rector now responsible for ninety percent of the country’s new jobs. In 1968, McDonald’s operated about 1,000 restaurants. Today it has about 23,000 restaurants worldwide and opens roughly 2,000 new ones each year. An estimated one of every eight Americans has worked at McDonald’s. The company annually trains more new workers than the U.S. Army. McDonald’s is the nation’s largest purchaser of beef and potatoes. It is the second-largest purchaser of poultry.