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问题 单项选择题

调节锅炉气压就是调节其( )。

A．燃料量

B．风量

C．给水量

D．蒸发量

答案

参考答案：D

解析：在锅炉运行中，蒸汽压力应基本上保持稳定。锅炉气压的变动通常是由负荷变动引起的，当锅炉蒸发量和负荷不相等时，气压就要变动。若负荷小于蒸发量，气压就上升，负荷大于蒸发量，气压就下降。所以，调节锅炉气压就是调节其蒸发量，而蒸发量的调节是通过燃烧调节和给水调节来实现的。

单项选择题

下图是某地区土地利用现状示意图(布局合理)，读图回答下列题。

适宜在P点布局的是（）。

A．钢铁厂

B．造纸厂

C．印染厂

D．自来水厂
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问答题

Exactly where we will stand in the long war against disease by the year 2050 is impossible to say. (46)But if developments in research maintain their current pace, it seems likely that a combination of improved attention to dietary and environmental factors, along with advances in gene therapy and protein targeted drugs, will have virtually eliminated most major classes of disease.
From an economic standpoint, the best news may be that these accomplishments could be accompanied by a drop in health-care costs. (47)Costs may even fall as diseases are brought under control using pinpointed, short term therapies now being developed. By 2050 there will be fewer hospitals, and surgical procedures will be largely restricted to the treatment of accidents and other forms of trauma. Spending on nonacute care, both in nursing facilities and in homes, will also fall sharply as more elderly people lead healthy lives until close to death.
One result of medicine’s success in controlling disease will be a dramatic increase in life expectancy. (48) The extent of that increase is a highly speculative matter, but it is worth that medical science has already helped to make the very old (currently defined as those over 85 years of age) the fastest growing segment of the population . Between 1960 and 1995, the U. S. population as a whole increased by about 45%, while the segment over 85 years of age grew by almost 300% . (49)There has been a similar explosion in the population of centenarians, with the result that survival to the age of 100 is no longer the newsworthy feat that it was only a few decades ago. U. S. Census Bureau projections already forecast dramatic increase in the number of centenarians in the next 50 years: 4 million in 2050, compared with 37,000 in 1990.
(50)Although Census Bureau calculations project an increase in average life span of only eight yeas by the year 2050, some exerts believe that the human life span should not begin to encounter any theoretical natural limits before 120 years. With continuing advances in molecular medicine and a growing understanding of the aging process, that limit could rise to 130 years or more.
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