The statistics in the first paragraph shows that _

单项选择题

The problems of the elderly are attracting greater attention largely because the American population is growing steadily older as the proportion of its aged members increase. At the time of the first United States census in 1790, half of the people in the country were 16 or younger. By the turn of the present century the median age of the population had risen to 22.9 years; by 1970, it was 27.7 ; and by 1977 it had reached 28.9 ; the median age will reach 35 by the year 2000, and will approach 40 by the year 2030.
In time the burden of the years affects even the healthiest individual. Aging is accompanied by physiological changes that are not necessarily the result of any disease: apart from the more obvious signs of age—such as baldness, wrinkling, changes in body form, and stiffness of limbs—there is a general process of atrophy of the cells and gradual degeneration. However, the rate of physiological aging varies greatly from one person to another. Some people show noticeable signs of aging as early as fifty. Others seem relatively young and vital at seventy, and may even continue to enjoy a vigorous sex life.
In general, however, ill health becomes more common with advancing age. More than three quarters of those over sixty-five suffer from some chronic health condition. But ill health need not have only physiological causes; it can have social and psychological causes as well. People tend to follow social expectations to fill the roles that are offered to them. In a sense, all we offer the aged is a sick role—the role of the infirm person who has outlived his or her usefulness to society. An urbanized, industrialized society such as the United States is oriented toward youth, mobility, and activity. It does little to integrate the old into the social structure.
Unlike the elders in a traditional society, the American aged can no longer lay automatic claim on their kin for support and social participation; on the contrary, they are more likely to have to try not to be a "nuisance" to their now independent adult offspring. Nor are they regarded as the wisest members of the community as the elders in a traditional society would be; instead, any advice they give is likely to be considered irrelevant in a changing world about which their descendants consider themselves much better informed.
In America, childhood is romanticised, youth is idolised, middle age does the work, wields the power and pays the bills, and old age gets little or nothing for what it has already done. For many elderly Americans old age is a tragedy, a period of quiet despair, deprivation, desolation and muted rage. The tragedy of old age is not that each of us must grow old and die but that the process of doing so has been made unnecessarily painful, humiliating and isolating through insensitivity, ignorance, and poverty.

The statistics in the first paragraph shows that ______.

A．American people are living longer
B．the definition of middle age is changing
C．the American society is becoming older
D．the age below 40 will be thought young by 2030