题目内容
（请给出正确答案）
A.Radius
B.Diameter
C.Dimension
D.Circumference
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更多“_____ is the length of the closed curve of a circle.”相关的问题
The idea of the "improvement factor" (Para. 3) implies roughly
A．wages should be paid on the basis of length of service
B．the benefit of the increased production and lower costs should be shared by workers
C．supplementary unemployment benefit plans should be promoted
D．the transition to automation should be brought about with tile minimum of inconvenience and distress to workers.
The word "springs" in Paragraph 3 means
A．a small stream of water flowing naturally from the earth.
B．the season of the year, occurring between winter and summer.
C．the act or an instance of jumping or leaping.
D．a length of metal wound around, which returns to its original shape after being pushed.
Books are steadily increasing in size: the average number of pages has grown by 25% over the last 15 years. A study of more than 2500 books appearing on New York Times bestseller reveals that the average length has increased from 320 pages in 1999 to 400 pages in 2014. According to James Finlayson, who carried out the survey, there ’s a “relatively consistent pattern of grow th year on year ”. For Finlayson, much of this shift can be explained by the industry ’s shift towards digital. He says “When you pick up a large book in a shop, you can sometimes be intimidated, but if you have a big book on a Kindle （eBook ）, that’s not a consideration. ”
SECTION B PASSAGES
Directions: In this section, you will hear several passages. Listen to the passages carefully and then answer the questions that follow.
听力原文： In ancient times, many people believed the earth was a flat disc. Well over 2,000 years ago, the ancient Greek philosophers were able to put forward two good arguments proving that it was not. Direct observation of heavenly bodies was the basis of both these arguments. First, the Greeks knew that during eclipses of the moon, the earth was between the sun and the moon, and they saw that during these eclipses, the earth's shadow on the moon was always round, they realized that this could be true only if the earth was spherical. If the earth were a flat disc, then its shadow during eclipses would not be a perfect circle, it would be stretched out into a long ellipse. The second argument was based on what the Greeks saw during their travels. They noticed that the North Star, or Polaris, appeared lower in the sky when they traveled south, in more northerly regions, the North Star appeared to them to be much higher in the sky. By the way, it was also from this difference in the apparent position of the North Star that the Greeks first calculated the approximate distance around the circumference of the earth, a figure recorded in ancient documents says 400,000 stadia, that's the plural of the word stadium. Today, it's not known exactly what length one stadium represents, but let's say it was about 200 meters, the length of many athletic stadiums. This would make the Greek's estimate about twice the figure accepted today, a very good estimate for those writing so long before even the fast telescope was invented.
According to the professor, what were, the beliefs of the Greek philosophers based upon？
A．How the natural world was described in Greek mythology.
B．What they observed directly.
C．The writings of philosophers from other societies.
D．Measurements made with scientific instruments,
根据以下内容回答题：
No one knows for sure why birds migrate．One theory of migration says that ancient birds of the northern part of the earth were forced southward during the Ice Age，when ice covered large parts of Europe，Asia and North America．As the ice melted，the birds came back to their homelands，spent the summer，and then went south again in winter．Gradually，these comings and goings became habits，and birds now migrate though much of the ice has gone．
Another theory proposes that the ancient home of all modern birds was the tropic areas．There lived so well that the region became overcrowded．Many species had to move northward．During the summer，these birds found plenty of room and food．In winter，however，food be-came scarce and they had to return to the south．
A newer theory is that increasing daylight stimulates certain glands(腺)in the bird’s body and prepares it for migration．One scientist is able to make birds migrate in midwinter by expo-sing them for two months to artificial daylight．Recoveries of marked birds indicate that they fly north as soon as they are set free．The conclusion is that the urge to migrate is determined by changes in the bird’s body which take place under seasonal changes in the length of daylight．
This theory would account for the fact that not all birds migrate at the same time．Each sDecies seems to have its own schedule．The theory would also account for the regular time and rou‘tes of migration．Birds arrive at a given place year after year．Unfavorable weather delays them only a few days．Total hours of daylight，rather than weather，start them on the way．
How birds find their way to the same place year after year and why they follow their own Darticular route are still mysteries．They evidently do not follow known landmarks，for many young birds migrate alone without the help of experienced adults．
We can conclude from the first paragraph that__________ ． 查看材料
A.during the Ice Age，the whole Europe was covered with ice
B.the south used to be the homelands of all birds
C.scientists can confidently explain why birds migrate now
D.migration of birds can be explained by the change of ice on earth
第三篇
Slowing Aging: Way to Fight Diseases in 21st Century
A group of aging experts from the United States and the United Kingdom suggest that the best strategy for preventing and fighting a multitude of diseases is to focus on slowing the biological processes of aging.
"The traditional medical approach of attacking individual diseases - cancer, diabetes, heart disease, Alzheimer's disease (早老性痴呆病) and Parkinson's disease (帕金森氏病) -will soon become less effective if we do not determine how all of these diseases either interact or share common mechanisms with aging," says S. Jay Olshansky, professor of epidemiology at the University of Illinois at Chicago School of Public Health and senior author of the commentary.
Middle-aged and older people are most often impacted by simultaneous but independent medical conditions. A cure for any of the major fatal diseases would have only a marginal impact on life expectancy (预期寿命) and the length of healthy life, Olshansky said.
The authors suggest that a new paradigm (模式) of health promotion and disease prevention could produce unprecedented social, economic and health dividends for current and future generations if the aging population is provided with extended years of healthy life.
They note that all living things, including humans, possess biochemical mechanisms that influence how quickly we age and, through dietary (饮食的) intervention or genetic alteration, it is possible to extend lifespan to postpone aging-related processes and diseases.
Further research in laboratory models is expected to provide clues to and deeper understanding of how existing interventions, such as exercise and good nutrition, may lead to lifelong well-being.
The authors also propose greatly increased funding for basic research into the
"fundamental cellular (细胞的) and physiological changes that drive aging itself."
"We believe that the potential benefits of slowing aging processes have been
underrecognized by most of the scientific community," said Olshansky. "We call on the health-research decision-makers to allocate substantial resources to support and develop practical interventions that slow aging in people."
An increase in age-related diseases and escalating health care costs make this the time for a "systematic attack on aging itself," the authors write.
Olshansky and colleagues contend that modern medicine is already heavily invested in efforts to extend life, and they argue that a fresh emphasis on aging has the potential to improve health and quality of life far more efficiently than is currently possible.
41 The experts believe the traditional approach of attacking individual diseases
A is the best strategy for fighting diseases.
B focuses on slowing aging processes.
C needs to be improved.
D has gone out of date.
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