单选题You must be tired, but try to hang on till all the work"s finished.

单选题Cell Phone Lets Your Secret Out Your cell phone holds secrets about you. Besides the names and (51) that you've programmed into it, traces of your DNA linger (逗留) on the device, according to a new study. DNA is genetic material that (52) in every cell. Like your fingerprint, your DNA is unique to you (53) you have an identical twin. Scientists today routinely analyze DNA in blood, saliva (唾液), or hair left (54) at the scene of a crime. The results often help detectives identify (55) and their victims. Your cell phone can reveal more about you (56) you might think. Meghan J. McFadden, a scientist at McMaster University in Hamilton, Ontario, heard about a crime in which the suspect bled onto a cell phone and later dropped the (57) . This made her wonder whether traces of DNA lingered on cell phones—even when no blood was involved (58) she and colleague Margaret Wallace of the City University of New York analyzed the flip-open phones of 10 volunteers. They used swabs (药签) to collect (59) traces of the users from two parts of the phone: the outside, where the user holds it, and the (60) , which is placed at the user's ear. The scientists scrubbed the phones using a solution made mostly (61) alcohol. The aim of washing was to remove all detectable traces of DNA. The owners got their phones (62) for another week. Then the researchers collected the phones and repeated the swabbing of each phone once more. The scientists discovered DNA that (63) to the phone's speaker on each of the phones. Better samples were collected from the outside of each phone, but those swabs also picked up DNA that belonged to other people who had apparently also handled the phone. (64) , DNA showed up even in swabs that were taken immediately after the phones were scrubbed (擦洗). That suggests that washing won't remove all traces of evidence from a criminal's device. So cell phones can now be added to the (65) of clues that can decide a crime-scene investigation.

单选题 Night of the Living Ants When an ant dies, other ants move the dead insect out of the nest. This behavior is interesting to scientists, who wonder how ants know for sure—and so soon—that another ant is dead. Dong-Hwan Choe, a scientist at the University of California found that Argentine ants have a chemical on the outside of their bodies that signals to other ants, "I'm dead—take me away." But there's a twist to Choe's discovery. These ants are a little bit like zombies (僵尸). Choe says that the living ants—not just the dead ones—have this death chemicals. In other words, while an ant crawls around, perhaps in a picnic or home, it's telling other ants that it's dead. What keeps ants from hauling away the living dead? Choe found that Argentine ants have two additional chemicals on their bodies, and these tell nearby ants something like, "Wait—I'm not dead yet," So Choe's research turned up two sets of chemical signals in ants: one says, "I'm dead," the other set says," I'm not dead yet." Other scientists have tried to figure out how ants know when another ant is dead. If an ant is knocked unconscious, other ants leave it alone until it wakes up. That means ants know that unmoving ants can still be alive. Choe suspects that when an Argentine ant dies, the chemical that says "Wait—I'm not dead yet" quickly goes away. Once that chemical is gone, only the one that says "I'm dead" is left. "It's because the dead ant no longer smells like a living ant that it gets carried to the graveyard (墓地), not because its body releases new unique chemicals after death," said Choe. When other ants detect the "dead" chemical without the "not dead yet" chemical, they haul away the body. This was Choe's hypothesis (假设). To test his hypothesis, Choe and his team put different chemicals on Argentine ant pupae (蛹). When the scientists used the "I'm dead" chemical, other ants quickly hauled the treated pupae away. When the scientists used the "Wait—I'm not dead yet" chemicals, other ants left the treated pupae alone. Choe believes this behavior shows that the "not dead yet" chemicals override (优先于) the "dead" chemical when picked up by adult ants. And that when an ant dies, the "not dead yet" chemicals fade away. Other nearby ants then detect the remaining "dead" chemical and remove the body from the nest.

单选题He was rather vague about the reasons why he never finished school.

单选题Sugar Power for Cell Phones Using enzymes commonly found in living cells, a new type of fuel cell produces small amounts of electricity from sugar. If the technology is able to succeed in mass production, you may some day share your sweet drinks with your cell phone. In fuel cells, chemical reactions generate electrical currents. The process usually relies on precious metals, such as platinum. In living cells, enzymes perform a similar job, breaking down sugars to obtain electrons and produce energy. When researchers previously used enzymes in fuel cells, they had trouble keeping them active, says Shelley D. Minteer of St Louis University. Whereas biological cells continually produce fresh enzymes, there's no mechanism in fuel cells to replace enzymes as they quickly degrade. Minteer and Tamara Klotzbach, also of St Louis University, have now developed polymers that wrap around an enzyme and preserve it in a microscopic pocket. "We tailor these pockets to provide the ideal microenvironment" for the enzyme, Minteer says. The polymers keep the enzyme active for months instead of days. In the new fuel cell, tiny polymer bags of enzyme are embedded in a membrane that coats one of the electrodes. When glucose from a sugary liquid gets into a pocket, the enzyme oxidizes it, releasing electrons and protons. The electrons cross the membrane and enter a wire through which they travel to the other electrode, where they react with oxygen in the atmosphere to produce water. The flow of electrons through the wire constitutes an electrical current that can generate power. So far, the new fuel cells don't produce much power, but the fact that they work at all is exciting, says Paul Kenis, a chemical engineer at the University of Illinois at Urhana-Champaign. "Just getting it to work," Kenis says, "is a major accomplishment." Sugar-eating fuel cells could be an efficient way to make electricity. Sugar is easy to find. And the new fuel cells that run on it are biodegradable, so the technology wouldn't hurt the environment. The scientists are now trying to use different enzymes that will get more power from sugar. They predict that popular products may be using the new technology in as little as 3 years.

单选题What is the Coolest Gas in the Universe? What is the coldest air temperature ever recorded on the Earth? Where was this low temperature recorded? The coldest recorded temperature on Earth was -91℃, which 1 in Antarctica(南极洲) in 1983. We encounter an interesting situation when we discuss temperatures in 2 . Temperatures in Earth orbit(轨道) actually range from about +120℃ to -120℃. The temperature depends upon 3 you are in direct sunlight or in shade. Obviously, -120℃ is colder than our body can 4 endure. The space temperatures just discussed affect only our area of the solar 5 . Obviously, it is hotter closer to the Sun and colder as we travel 6 from the Sun. Scientists estimate temperatures at Pluto are about -210℃. How cold is the lowest estimated temperature in the entire universe? Again, it depends upon your 7 . We are taught it is supposedly 8 to have a temperature below absolute zero, which is -273℃, at which atoms do not move. Two scientists, Cornell and Wieman, have successfully 9 down a gas to a temperature barely above absolute zero. They won a Nobel Prize in Physics in 2001 for their work—not a discovery, in this case. Why is the two scientists" work so important to science? In the 1920s, Satyendra Nath Bose was studying an interesting 10 about special light particles (颗粒) we now call photons (光子). Bose had trouble 11 other scientists to believe his theory, so he contacted Albert Einstein. Einstein"s calculations helped him theorize that atoms 12 behave as Bose thought—but only at very cold temperatures. Scientists have also discovered that ultra-cold (超冷) atoms can help them make the world"s atomic clocks even 13 accurate. These clocks are so accurate today they would only lose one second 14 six million years! Such accuracy will help us travel in space because distance is velocity times time(d=vt). With the long distances involved in space 15 , we need to know time as accurately as possible to get accurate distance.

单选题The park gave the whale to the Foundation and big contributions came from all parts of the world. A. dominations B. denotation C. donations D. signatures

单选题{{B}}第三篇{{/B}} {{B}}A Phone that Knows You're Busy{{/B}} It's a modem conundrum: you're too busy to be disturbed by incessant phone calls so you mm your cell phone off. But if you don't remember to turn it back on when you're less busy, you could miss some important calls. If only the phone knew when it was wise to interrupt you, you wouldn't have to turn it off at all. Instead, it could let calls through during spells of relative inactivity. A bunch of behavior sensors and a clever piece of software could do just that, by analyzing your behavior to determine if it's a good time to interrupt you. If built into a phone, the system may decide you're too busy and ask the caller to leave a message or ring back later. In a desktop computer, the system could stop instant messages or spain annoying you when you're busy. James Fogarty and Scott Hudson at Camegie Mellon University in Pennsylvania based their system on tiny microphones, cameras and touch sensors that reveal body language and activity. First they had to study different behaviors to find out which ones strongly predict whether your mind is interrupted. The potential "busyness" signals they focused on included whether the office doors were left open or closed, the time of day, if other people were with the person in question, how close they were to each other, and whether or not the computer was in use. The sensors monitored these and many other factors while four subjects were at work. At random intervals, the subjects rated how in term ptible they were on a scale ranging from "highly interruptible" to "highly not—term ptible". Their ratings were then correlated with the various behaviors. "It is a shotgun approach: we used all the indicators we could think of and then let statistics ferret out which were important," says Hudson. The model showed that using the keyboard, and talking on a landline or to someone else in the office correlated most strongly with how interruptible the subjects judged themselves to be. Interestingly, the computer was actually better than people at predicting when someone was too busy to be interrupted. The computer got it right 82 per cent of the time, humans 77 percent. Fogarty speculates that this might be because people doing the interrupting are inevitably biased towards delivering their message, whereas computers don't care. The first application for Hudson and Fogarty's system is likely to be in an instant messaging system, followed by office phones and cell phones. "There is no technological roadblock to it being deployed in a couple of years," says Hudson.

单选题The Forbidden Apple New York used to be the city that never sleeps. These days, it"s the city that never smokes, drinks or does anything naughty (at least, not in public). The Big Apple is quickly turning into the Forbidden Apple. If you wanted a glass of wine with your picnic in Central Park, could you have one? No chance. Drinking alcohol in public isn"t allowed. If you decided to feed the birds with the last crumbs (碎屑) of your sandwich, you could be arrested. It"s illegal if you went to a bar for a drink and a cigarette, that would be OK, wouldn"t it? Er... No. You can"t smoke in public in New York City. What"s going on? Why is the city that used to be so open-minded becoming like this? The mayor of New York is behind it all. He has brought in a whole lot of new laws to stop citizens from doing what they want, when they want. The press is shocked. Even the New York police have joined the argument. They recently spent $100,000 on a "Don"t blame the cop" campaign. One New York police officer said, "We raise money for the city by giving people fines for breaking some very stupid laws. It"s all about money." The result is a lot of fines for minor offences. Yoav Kashida, an Israel tourist, fell asleep on the subway. When he woke up, two police officers fined him because he had fallen asleep on two seats (you mustn"t use two seats in the subway). Elle and Serge Schroitman were fined for blocking a driveway with their car. It was their own driveway. The angry editor of Vanity Fair magazine, Graydon Carter, says, "Under New York City law it is acceptable to keep a gun in your place of work, but not an empty ashtray." He should know. The police came to his office and took away his ashtray (烟灰缸). But not all of the New York"s inhabitants are complaining. Marcia Dugatty, 72, said, "The city has changed for the better. If more cities had these laws, America would be a better place to live." Nixon Patricks, 38, a barman, said, "I like the new laws, if people smoked in here, we"d go home smelling of cigarettes." Recent figures show that New York now has fewer crimes per 100,000 people than 193 other US cities. And it"s true—it"s safe, cleaner and more healthy than before. But let"s be honest who goes to New York for its clean streets?

单选题It's in the Cards In recent years, more and more people have been paying for things with credit cards. There are now 565 million credit cards worldwide, but it doesn't stop there. Debit cards (电子记账卡) are being issued by banks, and store cards are being offered by many department stores. Bills and coins are gradually being replaced by "plastic money." In many countries, phone cards have been introduced for people to use in pay phones. In addition, cards made of paper are being replaced by plastic ones by many organizations and clubs. For example, if you belong to a sports club, your membership card may well be made of plastic. How safe is the plastic used to make these cards, though? Until now, most cards have been made from a plastic called PVC. While PVC is being produced, harmful chemicals are released into the atmosphere. One of the most dangerous chemicals that is released is dioxin, which is known to cause cancer in humans. A further problem is that, when a PVC card is thrown away, it is not biodegradable; this means that it does not "break down" and cannot be recycled. Obviously, recycling reduces pollution of the environment. The executive director of the environmental organization and charity Greenpeace, Peter Melchett, says, "If there is a solution to this-and an alternative then it would be madness not to use it." Greenpeace has found a solution and an alternative. Their new credit card is made entirely from a biodegradable plastic that uses plants. The card breaks down in around three months in soil; in this way, it is recycled. In contrast, a PVC card lasts for centuries. Greenpeace hopes that many organizations will soon follow their example and issue cards that do not threaten the public health.

单选题Have you talked to her lately ?

单选题In arithmetic, a number stands for the size of a set of things.

单选题Effects of Environmental Pollution If pollution continues to increase at the present rate, formation of aerosols (浮质) in the atmosphere will cause the onset (开始) of an ice age in about fifty years" time. This conclusion, reached by Dr S. I. Rasool and Dr S. H. Schneider of the United States Goddard Space Flight Centre, answers the apparently conflicting questions of whether an increase in the carbon dioxide (二氧化碳) content of the atmosphere will cause the Earth to warm up or increasing the aerosol content will cause it to cool down. The Americans have shown conclusively that the aerosol question is dominant. Two spectres haunting conservationists have been the prospect that environmental pollution might lead to the planet"s becoming unbearably hot or cold. One of these ghosts has now been laid because it seems that even an increase in the amount of carbon dioxide in the atmosphere to eight times its present value will produce an increase in temperature of only 2℃ which would take place over several thousand years. But the other problem now looms larger than ever. Aerosols are collections of small liquid or solid particles dispersed in air or some other medium. The particles are all so tiny that each is composed of only a few hundred atoms. Because of this they can float in the air for a very long time. Perhaps the most commonly experienced aerosol is industrial smog (烟雾) of the kind that plagued London in the 1950s and is an even greater problem in Los Angeles today. These collections of aerosols reflect the Sun"s heat and thereby cause the Earth to cool. Dr. Rasool and Dr. Schneider have calculated the exact effect of a dust aerosol layer just above the Earth"s surface in the temperature of the planet. As the layer builds up, the present delicate balance between the amount of heat absorbed from the Sun and the amount radiated from the Earth is disturbed. The aerosol layer not only reflects much of the Sun"s light but also transmits the infrared (红外线的) radiation from below. So, while the heat input to the surface drops, the loss of heat remains high until the planet cools to a new balanced state. Within fifty years, if no steps are taken to stop the spread of aerosols in the atmosphere, a cooling of the Earth by as much as 3.5℃ seems inevitable. If that lasts for only a few years it would start another ice age, and because the growing ice caps at each pole would themselves reflect much of the Sun"s radiation it would probably continue to develop even if the aerosol layer were destroyed. The only bright spot in this gloomy forecast lies in the hope expressed by Dr. Rasool and Dr. Schneider that nuclear power may replace fossil fuels in time to prevent the aerosol content of the atmosphere from becoming critical.

单选题Nitrogen is the most plentiful gas in the {{U}}atmosphere.{{/U}}

单选题They didn't want anyone to know about their romance.A. adventureB. mysteryC. poemD. love

单选题I haven"t achieved very much today.

单选题The police arrested the suspect yesterday and released him this morning.

单选题This is not typical of English, but is a feature of the Chinese language.

单选题 阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从 4个选项中选择1个最佳答案。 {{B}} Migrant (移民的) Workers{{/B}} In the past twenty years, there has been an increasing tendency for workers to move from one country to another. While some countries have restricted (限制) most {{U}}(51) {{/U}} to local people, others have attracted and welcomed migrant workers. This is particularly the case in the Middle East, {{U}}(52) {{/U}} increased oil incomes have enabled many countries to call in outsiders to improve local facilities (设施). Thus the Middle East has attracted oil-workers {{U}}(53) {{/U}} the U.S.A. and Europe. It has also brought in workers from many other countries, {{U}}(54) {{/U}} South Korea and Japan. In view of the difficult living and working {{U}}(55) {{/U}} in the Middle East, it is not surprising that the pay is high to attract suitable workers. Many engineers and technicians can {{U}}(56) {{/U}} at least twice as much money in the Middle East as they can in their own country, and this is a major {{U}}(57) {{/U}}. Sometimes a disadvantage has a compensating (补尝的) advantage. For example, the {{U}}(58) {{/U}} living conditions often lead to increased friendshipwhen workers have to {{U}}(59) {{/U}} on each other for safety and comfort. In a similar way, many migrant workers can save large sums of money partly because of the {{U}}(69) {{/U}} of entertainment (娱乐) facilities. The work is often complex and full of problems but this merely presents greater challenge to engineers who prefer to find solutions to problems rather than do {{U}}(61) {{/U}} work in their home country. One major problem which {{U}}(62) {{/U}} migrant workers in the Middle East is that their jobs are temporary ones. They are nearly always on {{U}}(63) {{/U}}, so it is not easy for them to plan ahead with great confidence. This is to be {{U}}(64) {{/U}} since no country welcomes a large number of foreign workers as permanent residents. In any {{U}}(65) {{/U}}, migrant Workers accept this disadvantage, along with others, because of the considerable financial benefits which they receive.

单选题{{U}}Practically{{/U}} all animals communicate through sounds. A. Almost B. Clearly C. Absolutely D. Basically