27. The new system does document retrieval by ____.

　　28. The new system is expected to improve precision in ____.

　　29. When performing document retrieval the existing search engines ignore __ __

　　30. The new system was found more effective in document search than the ____

　　A. using photos

　　B. description of the HTML page

　　C. current popular search engines

　　D. document search

　　E. information in images

　　F. machine vision systems

　　第4部分：阅读理解(第31—45题，每题3分，共45分)

　　下面有3篇短文，每篇短文后有5道题。请根据短文内容，为每题确定1个最佳选项。

　　第一篇 Face Masks May Not Protect from Super-Flu

　　IF a super-flu strikes, face masks may not protect you. Whether widespread use of masks will help, or harm, during the next worldwide flu outbreak is a question that researchers are studying furiously. No results have come from their mask research yet. However, the government says people should consider wearing them in certain situations anyway, just in case.

　　But it’s a question the public keeps asking while the government are making preparations for the next flu pandemic. So the Centers for Disease Control and Prevention (CDC) came up with preliminary guidelines. “We don’t want people wearing them everywhere,” said the CDC. “The overall recommendation really is to avoid exposure.”

　　When that’s not possible, the guidelines say to consider wearing a simple surgical mask if you are in one of the three following situations. First, you’re healthy and can’t avoid going to a crowded place. Second t you’re sick and think you may have close contact with the healthy, such as a family member checking on you. Third, you live with someone who’s sick and thus might be in the early stages of infection, but still need to go out.

　　Influenza pandemics can strike when the easy-to-mutate flu virus shifts to a strain that people never have experienced. Scientists cannot predict when the next pandemic will arrive, although concern is rising that the Asian bird flu might trigger one if it starts spreading easily from person to person.

　　During the flu pandemic, you should protect yourself. Avoid crowds, and avoid close contact with the sick unless you must care for someone. Why aren’t masks added to this self-protection list? Because they can help trap virus-laden droplets flying through the air with a cough or sneeze. Simple surgical masks only filter the larger droplets. Besides, the CDC is afraid masks may create a false sense of security. Perhaps someone who should have stayed home would don an ill-fitting mask and hop on the subway instead.

　　Nor does flu only spread through the air. Say someone covers a sneeze with his or her hand, then touches a doorknob or subway pole. If you touch that spot next and then put germy hands on your nose or mouth, you’ve been exposed. It’s harder to rub your nose while wearing a mask and so your face may get pretty sweaty under masks. You reach under to wipe that sweat, and may transfer germs caught on the outside of the mask straight to the nose. These are the problems face masks may create for their users.

　　Whether people should or should not use face masks still remains a question. The general public has to wait patiently for the results of the mask research scientists are still doing.

　　31. What is the passage mainly about?

　　A. Widespread use of face masks. B. Possibility of a worldwide flu outbreak

　　C. New discoveries of a face mask research. D. Effectiveness of wearing face masks

　　32. The CDC suggests that people

　　A. stay alone when being sick. B. wear face masks when going to a crowded place.

　　C. wear face masks wherever possible. D. remain at home if living with someone who’s sick.

　　33. The word "that" in Paragraph 3 refers to

　　A. making preparations. B. avoiding exposure

　　C. coming up with guidelines. D. wearing face masks everywhere.

　　34. Which of the following statements is true?

　　A. Scientists warn the next flu is coming soon.

　　B. Asian bird flu is spreading easily from person to person.

　　C. Masks protect people because they keep viruses away.

　　D. Masks are not effective if a flu strikes.

　　35. One of the concerns the CDC has is that

　　A .masks may give people a wrong assumption of being safe.

　　B. the sick may not wear masks and go out.

　　C. flu virus may spread via public transportation.

　　D. healthy people may not know how to protect themselves.

　　第二篇 What’s killing the Bats

　　First it was bees. Now it is bats. Biologists in America are working hard to discover the cause of the mysterious deaths of tens of thousands of bats in the northeastern part of the country. Most of the bats affected are the common little brown bats (Myotis lucifugus,) but other species, such as the long-eared bat, the small-footed hat, the eastern pipistrelle, and the Indiana bat have also been affected. In some caves, more than 90 percent of the bat populations have died.

　　One possibility is disease. A white fungus (真菌)known as fusarium has been found on the noses of both living and dead bats. However, scientists don't know If the fungus is the primary cause of death, a secondary cause of death, or not a cause at all, but the result of some other conditions.

　　Another possible cause is a lack of food. For example, bats typically eat a large number of moths (蛾), and in some states such as New York, the number of moths has been declining in recent years. If bats can’t eat enough food, they starve to death.

　　Still other scientists believe that global warming is to blame. Warmer temperatures in recent years have been waking up hibernating (冬眠)bats earlier than usual. If bats break their hibernation at the wrong time, they might not find their expected food sources. The weather might also turn cold again and weaken or kill the bats.

　　Scientists might not agree on the causes of the bat die-off, but they do agree on the consequences. Bats are an important predator of mosquitoes; a single brown bat can eat 1,000 or more insects in an hour. They also eat beetles and other insects that damage plant crops. If there aren't enough bats, damage will be great from the insects they eat While bats live a long time for their size 一 the little brown bat can live for more than 30 years 一 a female bat has only one baby per year, so bat populations grow slowly. Many bat species in the United States are already protected or endangered.

　　How can you help? Do not disturb sleeping or nesting bats. If you discover bate that seem to be sick or that are dead, contact your local Fish& Wildlife Department with the details. However, be careful not to touch the animals.

　　36. What is the main idea of this passage?

　　A. All species of bats in North America are dying.

　　B. Scientists already know the cause of the deaths of bats

　　C. The bat deaths are a serious problem.

　　D. There are many possible causes of the deaths of bats.

　　37. What does the first sentence in Paragraph 1 mean?

　　A. Bees have been dying mysteriously.

　　B. The first article on the website is about bees.

　　C. Bees usually die before bats.

　　D. It was bees that caused the deaths of bats.

　　38. The word “pipistrelle" in Paragraph 1 refers to

　　A. a kind of fungus. B. an area in the U.S. C. a special cave. D. a kind of bat.

　　39. The "moths" in Paragraph 3 are taken as an example of

　　A. diseases that kill bats. B. Insects that bats eat.

　　C. animals that have diseases. D. bat species that are starving to death.

　　40. What is the purpose of the last paragraph?

　　A. To get people to stop killing bats. B. To hire workers for the Fish & Wildlife Department.

　　C. To ask people not to touch dead bats. D. To tell the public how to help bats.

　　第三篇 Better Solar Energy Systems: More Heat, More Light

　　Solar photovoltaic thermal energy systems, or PVTs, generate both heat and electricity, but until now they haven’t been very good at the heat-generating part compared to a stand-alone solar thermal collector. That’s because they operate at low temperatures to cool crystalline silicon solar cells, which lets the silicon generate more electricity but isn’t a very efficient way to gather heat.

　　That’s a problem of economics. Good solar hot-water systems can harvest much more energy than a solar-electric system at a substantially lower cost. And it’s also a space problem： photovoltaic cells can take up all the space on the roof, leaving little room for thermal applications.

　　In a pair of studies, Joshua Pearce, an associate professor of materials science and engineering, has devised a solution in the form of a better PVT made with a different kind of silicon. His research collaborators are Kunal Girotra from ThinSilicon in California and Michael Pathak and Stephen Harrison from Queen’s University, Canada.

　　Most solar panels are made with crystalline silicon， but you can also make solar cells out of amorphous silicon, commonly known as thin-film silicon. They don’t create as much electricity, but they are lighter, flexible, and cheaper. And, because they require much less silicon, they have a greener footprint. Unfortunately，thin-film silicon solar cells are vulnerable to some bad-news physics in the form of the Staebler-Wronski effect.

　　“That means that their efficiency drops when you expose them to light — pretty much the worst possible effect for a solar cell,” Pearce explains，which is one of the reasons thin-film solar panels make up only a small fraction of the market.

　　However, Pearce and his team found a way to engineer around the Staebler-Wronski effect by incorporating thin-film silicon in a new type of PVT. You don’t have to cool down thin-film silicon to make it work. In fact，Pearce’s group discovered that by heating it to solar-thermal operating temperatures，near the boiling point of water, they could make thicker cells that largely overcame the Staebler-Wronski effect. When they applied the thin-film silicon directly to a solar thermal energy collector, they also found that by baking the cell once a day，they boosted the solar cell’s electrical efficiency by over 10 percent.

　　41. PVTs are not efficient in

　　A. creating electricity. B. cooling silicon solar cells.

　　C. generating heat. D. powering solar thermal collectors.

　　42. One of the problems PVTs have is that

　　A. their thermal applications are costly. B. they are too expensive to afford.

　　C. they occupy too much space. D. it is hard to fix them on the roof.

　　43. Which of the following is NOT mentioned as an advantage of thin-film silicon solar cells?

　　A. They are electrically efficient. B. They are less expensive.

　　C. They are flexible. D. They are environment friendly.