单选题Which of the following could not be defined as combustion?

单选题The human Y chromosome--the DNA chunk that makes a man a man--has lost so many genes over evolutionary time that some scientists have suspected it might disappear in 10 million years. But a new study says it'll stick around. Researchers found no sign of gene loss over the past 6 million years, suggesting the chromosome is "doing a pretty good job of maintaining itself," said researcher David Page of the Whitehead Institute for Biomedical Research in Cambridge, Mass. That agrees with prior mathematical calculations that suggested the rate of gene loss would slow as the chromosome evolved, Page and study co-authors note in Thursday's issue of the journal Nature. And, they say, it clashes with what Page called the "imminent demise" idea that says the Y chromosome is doomed to extinction. The Y appeared 300 million years ago and has since eroded into a dinky chromosome, because it lacks the mechanism other chromosomes have to get rid of damaged DNA. So mutations have disabled hundreds of its original genes, causing them to be shed as useless. The Y now contains only 27 genes or families of virtually identical genes. In 2003, Page reported that the modern-day Y has an unusual mechanism to fix about half of its genes and protect them from disappearing. But he said some scientists disagreed with his conclusion. The new paper focuses on a region of the Y chromosome where genes can't be fixed that way. Researchers compared the human and chimpanzee versions of this region. Humans and chimps have been evolving separately for about 6 million years, so scientists reasoned that the comparisons would reveal genes that have become disabled in one species or the other during that time. They found five such genes on the chimp chromosome, but none on the human chromosome, an imbalance Page called surprising. "It looks like there has been little if any gene loss in our own species lineage in the last 6 million years," Page said. That contradicts the idea that the human Y chromosome has continued to lose genes so fast it'll disappear in 10 million years, he said. "I think we can with confidence dismiss ... the 'imminent demise' theory," Page said. Jennifer A. Marshall Graves of the Australian National University in Canberra, a gene researcher who argues for eventual extinction of the Y chromosome, called Page's work "beautiful" but said it didn't shake her conviction that the Y is doomed. The only real question is when, not if, the Y chromosome disappears, she said. "It could be a lot shorter than 10 million years, but it could be a lot longer," she said. The Y chromosome has already disappeared in some other animals, and "there's no reason to expect it can't happen to humans," she said. If it happened in people, some other chromosome would probably take over the sex-determining role of the Y, she said.

单选题 Scientists around the world are racing to learn how to rapidly diagnose, treat and stop the spread of a new, deadly disease. SARS — Severe Acute Respiratory Syndrome — was{{U}} (1) {{/U}}for the first time in February 2003 in Hanoi,{{U}} (2) {{/U}}since then has infected more than 1,600 people in 15 countries, killing 63. At this{{U}} (3) {{/U}}, there are more questions than answers surrounding the disease. Symptoms start{{U}} (4) {{/U}}a fever over 100.4 degrees F, chills, headache or body{{U}} (5) {{/U}}. Within a week, the patient has a dry cough, which might{{U}} (6) {{/U}}to shortness of breath. In 10% to 200% of cases, patients require{{U}} (7) {{/U}}ventilation to breathe. About 3.5% die from the disease. Symptoms{{U}} (8) {{/U}}begin in two to seven days, but some reports suggest it{{U}} (9) {{/U}}take as long as 10 days. Scientists are close to{{U}} (10) {{/U}}a lab test to diagnose SARS. In the meantime, it is diagnosed by its symptoms. There is no evidence{{U}} (11) {{/U}}antibiotics or anti-viral medicines help,{{U}} (12) {{/U}}doctors can offer only supportive care. Patients with SARS are kept in isolation to reduce the risk of{{U}} (13) {{/U}}. Scientists aren’t sure yet, but some researchers think it’s a{{U}} (14) {{/U}}discovered coronavirus, the family of viruses that cause some common colds. Most cases appear to have been passed{{U}} (15) {{/U}}droplets expelled when infected patients cough or sneeze. Family members of infected people and medical workers who care for them have been most likely to{{U}} (16) {{/U}}the illness. But recent developments in Hong Kong suggest that the{{U}} (17) {{/U}}might spread through air, or that the virus might{{U}} (18) {{/U}}for two to three hours on doorknobs or other{{U}} (19) {{/U}}Health experts say it is{{U}} (20) {{/U}}, though, that sharing an elevator briefly with an infected person would be enough to pass the virus.

单选题What kind of women do "curvaceous women" (Line 3, Para. 1) most probably refer to?

单选题Because of changes in economy and technological evolution challenge, vocational education has to ______.

单选题Our purpose of educating children is to______.

单选题The dot-com collapse may have been a disaster for Wall Street, but here in Silicon Valley, it was a blessing. It was the welcome end to an abnormal condition that very nearly destroyed the area in an overabundance of success. You see, the secret to the Valley's astounding multiple-decade boom is failure. Failure is what fuels and renews this place. Failure is the foundation for innovation. The valley's business ecology depends on failure the same way the tree-covered hills around us depend on fire--it wipes out the old growth and creates space for new life. The valley has always been in danger of drowning in the unwelcome waste products of success--too many people, too expensive houses, too much traffic, too little office space and too much money chasing too few startups. Failure is the safety valve, the destructive renewing force that frees up people, ideas and capital and recombines them, creating new revolutions. Consider how the Internet revolution came to be. After half a decade of start-up struggles, for example, hundreds of millions of Hollywood dollars were going up in smoke. It all seemed like a terrible waste, but no one noticed that the collapse left one very important byproduct, a community of laid-off C++ programmers who were now expert in multimedia design, and out on the street looking for the next big thing. These media geeks were the pioneer of the dot-com revolution. They were the Web's business pioneers, applying their newfound media sensibilities to create one little company after another. Most of these start-ups failed, but even in failure they advanced the new medium of cyberspace. A few geeks, like Silicon Graphics founder Jim Clark, succeeded and utterly changed our lives. In 1994 Clark was unemployed after leaving the company be founded, doggedly trying to develop a new interactive-TV concept. He approached Marc Andreessen, the co-developer of Mosaic, the first widely used Internet browser, in hope of persuading Andreessen to help him de-sign his new system. Instead, Andreessen opened Clark's eyes to the Web's potential. Clark promptly tossed his TV plans in the trash, and the two co-founded Netscape, the cornerstone of the consumer-Web revolution. Like the interactive-TV refugees and generations of innovators before them, the dot comers are already hatching new companies. Many are revisiting good ideas executed badly in the' 90s, while others are striking out into entirely new spaces. This happy chaos is certain to mature into a new order likely to upset an establishment, as it delivers life-changing wonders to the rest of us. But this is just the start, for revolutions give birth to revolutions. So let's hope for more of Silicon Valley's successful failures.

单选题{{B}}Text 4{{/B}} A recent article in The New York Times noted that Hollywood types now are wearing flip-flops(拖鞋)-- shoes appropriate for beachcombers--to business meetings. Decades ago, Californians were forgiven their sloppy attire as unique to their somewhat {{U}}frivolous{{/U}} culture. Elsewhere during that bygone era, people were careful how they dressed when seen in public and certainly when going to the office. No one would think of traveling by plane in shorts or wearing anything but their best clothes for attending a church service, concert, wedding, or funeral. Look at old newsreels of baseball games and you will see most of the men in a shirt and tie. Walk through an airport today and you have to strain to find a man wearing a jacket (forget the shirt and tie) or a woman in a nice shirt. If so, they clearly are over 60. The standard for dressing down continues to decline. Neckties and suits no longer are fashionable; male models think it cool to have a face full of stubble(胡子茬). A rock star slouches onto the stage in his undershirt. Think about it: Dean Martin never failed to appear in Las Vegas in anything but his tux, and Frank Sinatra always was dressed to the nines when seen in public. That was the standard. Dress reflects many things about us and our culture. It tells us about standards, deportment, pride, and character. Somewhere along the way, our elites lost their self-confidence. Codes of dress fell by the wayside and, with them, standards of language and behavior. In a world stable and peaceful with no enemies lurking in the shadows to do us unspeakable harm, why would it matter what standards of courtesy we follow? Life would go on as it is. Sadly, this is not a relaxed era such as the 1990s. It matters now what kind of the society we are. We must recapture the seriousness of a generation that won World War II and persevered through the Cold War. We may be involved in a struggle even more lengthy, deadly, and demanding than the Cold War. The watchwords must be sacrifice, vigilance, and determination. A sloppy, self-indulgent culture will not produce an effective effort against an enemy as fanatical as the Japanese Kamikaze(日本神风敢死队) pilots. Our seriousness in World War II and the early Cold War reflected the qualities of a generation of American leaders, embodying the virtues of public spiritedness, selflessness, courage, and integrity. These leaders were human and made mistakes, but they set the tone for an entire era. Their tough-minded policies and dignified appearance reflected their character. That is why it matters how we present ourselves in public. For in a time as serious as theirs-- and ours-- it is character that eventually will triumph.

单选题When an associate of the Mus6e d"Art Moderne Andr6-Malraux in Normandy flipped through the catalogue for the auction of impressionist art at Sotheby"s in New York on November 2nd, he made a startling discovery. On sale was "Blanchisseuses souffrant des dents", a painting by Edgar Degas, which had been stolen in 1973 from a museum where it had been on loan from the Louvre. After being alerted by the French authorities, Sotheby"s dropped the painting from the sale. Now an investigation is under way. The owner is likely to lose it without compensation when it is returned to France. Like most art collectors, the owner had no art-title insurance, which would have provided compensation for the painting"s value. "Theft accounts for only a quarter of title disputes," says Judith Pearson, a co-founder of ARIS, a small insurance firm that has been selling title insurance since 2006 and which was taken over by Argo Group, a bigger insurer, earlier this month. Three-quarters of squabbles occur in cases of divorce or inheritance. A work of art may also carry liens after being used as a collateral for a loan. More rarely, two or more artists may collaborate but then disagree about who has authority to flog their co-production. Does the risk of title disputes warrant the cost of title insurance? ARIS charges a one-off premium of between 1.75% and 6% of the art"s value. In return the company will cover the legal costs in case of a title dispute and compensate for the agreed value of the art if their client loses the ownership dispute. ARIS has so far written about 1,000 policies and has not yet had a claim. An alternative to art-title insurance is for collectors to do due diligence about the provenance of a work of art themselves. Yet many do not have the time or the tools to carry out such research, which is a complex undertaking as there is no central register of art ownership. And even sophisticated collectors get it wrong, as the clients of Salander-O"Reilly, a New York art gallery, discovered. It collapsed spectacularly in 2007 after it emerged that it had dealt in stolen art and defrauded its clients in a Madoffian manner for years. Such cases are exceptional, but as the market booms and the value of art increases, more art lovers will look for additional assurances that their art is really theirs.

单选题The haunting paintings of Helene Schjerfbeck, on show in the final leg of a travelling tour that has already attracted thousands of visitors in Hamburg and The Hague, may come as a surprise to many. Few outside the Nordic world would recognise the work of this Finnish artist who died in 1946． More people should. The 120 works have at their core 20 self-portraits, half the number she painted in all. The first, dated 1880, is of a wide-eyed teenager eager to absorb everything. The last is a sighting of the artist's ghost-to-be; Schjerfbeck died the year after it was made. Together this series is among the most moving and accomplished autobiographies-in-paint. Precociously gifted, Schjerfbeck was 11 when she entered the Finnish Art Society's drawing school. "The Wounded Warrior in the Snow", a history painting, was bought by a private collector and won her a state travel grant when she was 17．Schjerfbeck studied in Paris, went on to Pont-Aven, Brittany, where she painted for a year, then to Tuscany, Cornwall and St Petersburg. During her 1887 visit to St Ives, Cornwall, Schjerfbeck painted "The Convalescent". A child wrapped in a blanket sits propped up in a large wicker chair, toying with a sprig. The picture won a bronze medal at the 1889 Paris World Fair and was bought by the Finnish Art Society. To a modern eye it seems almost sentimental and is redeemed only by the somewhat stunned, melancholy expression on the child's face, which may have been inspired by Schjerfbeck's early experiences. At four, she fell down a flight of steps and never fully recovered. In 1890, Schjerfbeck settled in Finland. Teaching exhausted her, she did not like the work of other local painters, and she was further isolated when she took on the care of her mother (who lived until 1923). "If I allow myself the freedom to live a secluded life", she wrote, "then it is because it has to be that way. " In 1902, Scherfbeck and her mother settled in the small, industrial town of Hyvinkaa, 50 kilometers north of Hetsinki. Isolation had one desired effect for it was there that Schjerfbeck became a modern painter. She produced still lives and landscapes but above all moody yet incisive portraits of her mother, local school girls, women workers in town (profiles of a pensive, aristocratic looking seamstress dressed in black stand out ). And of course she painted herself. Comparisons have been made with James McNeill Whistler and Edvard Munch. But from 1905, her pictures became pure Schjerfbeck. "I have always searched for the dense depths of the soul, that have not yet discovered themselves", she wrote, "where everything is still unconscious-there one can make the greatest discoveries. " She experimented with different kinds of underpainting, scraped and rubbed, made bright rosy red spots; doing whatever had to be done to capture the subconscious-her own and that of her models. In 1913, Schjerfbeck was rediscovered by an art dealer and journalist, Gosta Stenman. Once again she was a success. Retrospectives, touring exhibitions and a biography followed, yet Schjerfbeck remained little known outside Scandinavia. Th_at may have had something to do with her indifference to her renown. "I am nothing, absolutely nothing", she wrote. "All I want to do is paint". Schjerfbeck was possessed of a unique vision, and it is time the world recognised that.