以金红石（主要成分TiO2）为原料生产金属钛的步骤主要有： （1）在高温下，向金

关于人民币的发行，说法不正确的是

A．在一定时期内发行多少人民币是由国家决定的

B．人民币的面值是由国家决定的

C．每种面值的人民币发行量是由国家决定的

D．人民币的实际购买力是由国家决定的

继发闭经，发生于产后大出血后，伴随第二性征萎缩，孕激素试验阴性，应诊断为

A．子宫性闭经
B．卵巢性闭经
C．垂体性闭经
D．下丘脑性闭经
E．生理性闭经

DBF中有20条记录，在Visual FoxPro命令窗口中执行以下命令序列，最后显示的结果是______。 USETXL SKIP3COUNTTOn n

A．0

B．3

C．4

D．20

密钥的生存周期是指 【17】 使用该密钥的周期。

The most damning thing that can be said about the world’s best-endowed and richest country is that it is not only not the leader in health status, but that it is so low in the ranks of the nations. The United States ranks 18th among nations of the world in male life expectancy at birth, 9th in female life expectancy at birth, and 12th in infant mortality. More importantly, huge variations are evident in health status in the United States from one place to the next and from one group to the next.

The forces that affect health can be divided into four groupings that lend themselves to analysis of all health problems. Clearly the largest group of forces resides in the person’s environment. Behavior, in part derived from experiences with the environment, is the next greatest force affecting health. Medical care services, treated as separate from other environmental factors because of the special interest we have in them, make a modest contribution to health status. Finally, the contributions of heredity to health are difficult to judge.

No other country spends what we do per capita for medical care. The care available is among the best technically, even if used too freely and thus dangerously. Given the evidence that medical care is not that valuable and access to care not that bad, it seems most unlikely that our bad showing is caused by the significant proportion who are poorly served. Other hypotheses have greater explanatory power: excessive poverty, both actual and relative, and excessive wealth.

Excessive poverty is probably more prevalent in the U. S. than in any of the countries that have a better infant mortality rate and female life expectancy at birth. This is probably true also for all but four or five of the countries with a longer male life expectancy. In the notably poor countries that exceed us in male survival, difficult living conditions are a more accepted way of life and in several of them, a good basic diet, basic medical care and basic education, and lifelong employment opportunities are an everyday fact of life. In the U. S. a national unemployment level of 10 percent may be 40 percent in the ghetto while less than 4 percent elsewhere. The countries that have surpassed us in health do not have such severe problems. Nor are such a high proportion of their people involved in them.

Excessive wealth is not so obvious a cause of ill health, but, at least: until recently, few other nations could afford such unhealthful ways of living. Excessive intake of animal protein and fats, and use of tobacco and drugs, and dangerous recreational sports and driving habits are all possible only when one is wealthy. Our heritage, desires, and opportunities, combined with the relatively low cost of bad foods and speedy vehicles, make us particularly vulnerable. Our unacceptable health status, then, will not be improved appreciably by expanded medical resources nor by their redistribution so much as by a general attempt to improve the quality of life for all.

Which of the following questions does the passage provide information to answer（）

A. What is the most powerful influence on the health status of a population

B. Which nation in the world leads in health status

C. Is the life expectancy of males in the U.S. longer than that of females

D. What are the most important genetic factors influencing the health of an individual