单项选择题
The United States population is growing older. In 1987, 12 percent of Americans were 65 years old or older, compared with 8 percent in 1950. Population experts at the U.S. Bureau of the Census expect this percentage to continue to rise gradually, reaching 14 percent in 2010, then to skyrocket during the next 20 years, reaching 21 percent by 2030. This "graying of America" has generated concerns about whether the best really is yet to be, about how well off tomorrow’s elderly will be. There also are questions about the impact of an aging population on the rest of society.
The graying of America has two causes. First, advances in medical care have enable people to live longer. In the United States in 1900, the average life expectancy at birth was 47.7 years. By 1985, the latest year for which figures are available, it has climbed to 74.7 years.
Second, the U.S. birthrate rose in the mid-1900s, interrupting a long, slow decline. A dramatic increase occurred during this brief rise. From 1945 to 1947, the rate jumped from 20.4 births for every 1,000 people to 26.6. In 1957, the birthrate was still high — 25.3 — but then began to decline. The birthrate dropped to the 1933 level of 18.4 in 1966, andby 1985, was 15.7. Most experts see little change in the downward trend of the birthrate in the foreseeable future.
A. The long-range decline in the birthrate will continue in the next century.
B. Another dramatic increase in the birthrate will occur before the 21st century.
C. The birthrate will continue to vary greatly.
D. An increase in the birthrate depends mainly on advances in medical care.