加速坡 accelerating grade

The effect of the baby boom on the schools helped to make possible a shift in thinking about the role of public education in the 1920’s. In the 1920’s, but especially (1) the Depression of the 1930’s, the United States experienced a (2) birth rate. Then with the prosperity (3) on by the Second World War and the economic boom that followed it, young people married and (4) households earlier and began to (5) larger families than had their (6) during the Depression. Birth rates rose to 102 per thousand in 1946, 106.2 in 1950, and 118 in 1955. (7) economics was probably the most important (8) , it is not the only explanation for the baby boom. The increased value placed (9) the idea of the family also helps to (10) this rise in birth rates. The baby boomers began streaming (11) the first grade by the mid-1940’s and became a (12) by 1950. The public school system suddenly found itself (13) The wartime economy meant that few new schools were buih between 1940 and 1945. (14) , large numbers of teachers left their profession during that period for better-paying jobs elsewhere.
(15) , in the 1950’s, the baby boom hit an antiquated and inadequate school system. Consequently, the custodial rhetoric of the 1930’s no longer made (16) ; keeping youths ages sixteen and older out of the labor market by keeping them in school could no longer be a high (17) for an institution unable to find space and staff to teach younger children. With the baby boom, the focus of educators (18) turned toward the lower grades and back to basic academic skills and (19) . The system no longer had much (20) in offering nontraditional, new, and extra services to older youths.

A:accelerating B:strengthening C:declining D:fluctuating

Could HIV, the virus that causes AIDS, be weakening The results of a study conducted in Belgium, at the Institute of Tropical Medicine in Antwerp, seem to suggest that in one corner of the world it might be. The report, published in the latest issue of AIDS, a specialist journal, concludes that HIV’s ability to replicate (known technically as its virulence) may have decreased since the start of the pandemic. Kevin Aden, the lead author of the paper, stresses that the study is based on a small set of samples and does not prove that HIV’s virulence is attenuating around the world. However, it does offer new insights into the evolution of the disease.
Dr. Arien looked at 24 blood samples collected from untreated patients attending an HIV/ AIDS clinic in Antwerp. A dozen of these samples were taken between 1986 and 1989; the other 12 were collected between 2002 and 2003. First, he analyzed the samples to find their viral load (the number of virus particles per cubic centimeter) and the subtype of virus involved. In Europe and North America, the predominant subtype is B; in sub-Saharan Africa, where the epidemic is at its worst, the predominant subtype is C. Most of Dr. Arien’s samples were of subtype B. Having done this analysis, he paired the samples off for a series of replicative "duels". Each sample from the earlier series was matched with the most similar one from the later series, and they were placed in identical cell cultures to see which would multiply the most. The result was that 75% of the viruses from 2002-03 were less virulent than apparently similar counterparts from 1986-89 -- a statistically significant observation.
Dr. Arien’s caution is sensible, at least until someone replicates the work elsewhere. But his conclusion is not necessarily surprising. Such viral attenuation, as it is known, is one way that vaccines are produced.
What causes attenuation in wild viruses, though, is a matter of speculation. Dr Arien believes that in this case the attenuation could be the result of what he calls "serial genetic bottlenecks" during transmission from host to host. These act to reduce the genetic diversity (and thus the replicative fitness) of the virus. Genetic diversity is known to be an important component of HIV’s virulence. But what might cause the bottlenecks is still unclear.
A second reason for caution besides the small size of the study is, as Geoffrey Garnett, a professor of microparasite epidemiology at Imperial College, London, points out, that the ability of a virus to infect cells in a test-tube is not the same as its ability to cause disease and death in a human host. Nevertheless, Dr Aden’s result is intriguing, and surely worth following up in a larger piece of research.

A:weakening. B:accentuating. C:accelerating. D:increasing.

Foreign military aid was {{U}}prolonging{{/U}} the war.

A:broadening B:worsening C:extending D:accelerating

Foreign military aid was prolonging the war.（　）

A:broadening B:worsening C:extending D:accelerating

New Technique Promises Earlier Cancer Detection A new technique could revolutionize the early detection of cancer, giving sufferers a greater chance of beating the disease, American scientists said. Researchers at the Massachusetts Institute of Technology have devised a novel method of 【51】 changes in the nucleus of cells in the earliest stages of the disease." More than 85 percent of all cancers originate in the epithelium (上皮) that lines the internal surfaces of organs 【52】 the body. Although these are treatable 【53】 they are diagnosed in one of the preventable stages, early body damages are almost 【54】 to detect," said scientist Feld. " We present a new optical-probe (光学探子) technique based on light-scattering spectroscopy (分光镜检查) that is able 【55】 detect precancerous and early cancerous cells in cell-rich epithelia," he added in a statement. The new technique relies on the fact 【56】 cell nuclei change in the early stages of cancer and the differences scatter light in a characteristic way. Until now the changes were only detectable 【57】 a biopsy (活检) was taken, the scientists said. The new technique, 【58】 in the science journal Nature, can be used in conjunction with a routine cancer screening and surveillance technique which uses an endoscope (内窥镜) —a flexible optical probe 【59】 with cameras which is inserted into a cavity in the body—to check 【60】 cancers. The scientists said they 【61】 their new technique in four different organs during routine endoscopic cancer screening. The tip of the optical probe was brought into contact with the tissue to be tested and the scattering of light was recorded without the need for any tissue to be 【62】 , the scientists said. " Our results show that light-scattering spectroscopy has the potential to detect pre-cancerous body damages and preinvasive cancers throughout the body. This technique should 【63】 improve the efficiency of cancer screening and surveillance," the scientists said. Cancer is one of the biggest 【64】 in industrialized countries. 【65】 to figures from the World Health Organization, 10 million people were diagnosed with the disease worldwide in 1997 and six million died.

A:stopping B:accelerating C:delaying D:detecting

Foreign military aid was prolonging the war.

A:broadening B:worsening C:extending D:accelerating

Foreign military aid was {{U}}prolonging{{/U}} the war.

A:broadening B:worsening C:extending D:accelerating