单选题If you continue to indulge in computer games like this, your future will be {{U}}at stake{{/U}}.

单选题The {{U}}conquest{{/U}} has been the subject of much conjecture.

单选题"This light is too ______ for me to read by. Don't we have a brighter bulb?" said the elderly man.

单选题Last year, physicist Professor Richard Muller and colleagues published results from a new project analyzing the Earth"s temperature record. The Berkeley Earth Surface Temperature (BEST) project basically backed up established temperature records from Nasa and others; the world is indeed warming, and by about as much as we previously thought, it concluded. Professor Muller was attacked in some quarters for not waiting for the formal process of peer review in a scientific journal before launching the data publicly. He responded that his method—to put the draft out there openly and let everyone respond who wants to—is increasingly the norm in physics. In his view, it"s the right way to do things. A couple of weeks ago, in a New York Times article accompanying the release of five more BEST papers that are being submitted to scientific journals, Professor Muller went further, saying that the majority of 20th Century warming could be laid at the door of greenhouse gas emissions. By contrast, analysis by established bodies such as the Intergovernmental Panel on Climate Change (IPCC) holds that only after mid-Century did greenhouse gases drive the warming—prior to that, it was predominantly down to natural causes such as solar cycles and a decline in the frequency of large volcanoes.

单选题The last mayor was assassinated when he was fifty years old.

单选题Annie's job as an assistant at the university observatory was to classify stars according to their spectr

单选题A: I'm anxious to get started on my project. Can we discuss it sometime before the weekend?B: ______

单选题A: A young man from AT&T would like to talk with the manager on the new project. Is she available? B: ______.

单选题Ted: I ate four hamburgers, Morn. Mother: Well, you've made a pig of yourself. Question: What do we learn from the conversation?

单选题The river burst its banks, ______ an entire village.

单选题A: I have an appointment to see Dr. Gram for a physical examination. B: ______.

单选题Difference in position adopted by oxygen and hydrogen atoms account for variations in the crystalline structure of different forms of ice.

单选题Tom is reliable, so you can {{U}}count on{{/U}} him.

单选题Many students today display a {{U}}disturbing{{/U}} willingness to choose institutions and careers on the basis of earning potential.

单选题The unpopular measure finally ______ the downfall of the government.

单选题Woman: Grey says he's going to take three extra classes.Man: He's got to be kidding.Question: What does the man mean?

单选题{{B}}Passage Five{{/B}} In 1999 when MiShel and Carl Meissner decided to have children, they tackled the next big issue: Should they try to have a girl? It was no small matter. MiShel's brother had become blind from a hereditary condition in his early 20s, and the Meissners had learned that the condition is a disorder passed from mothers to sons. If they had a boy, he would have a 50 per cent chance of having the condition. A girl would be unaffected. The British couple's inquiries about sex selection led them to Virginia, US, where a new sperm-separation technique, called MicroSort, was experimental at the time. When MiShel became pregnant she gave birth to a daughter. Now they will try to have a second daughter using the same technique. The technique separates sperm into two groups—those that carry the X-chromosome (染色体) producing a female baby and those that carry the Y-chromosome producing a male baby. The technology was developed in 1990s, but the opening of a laboratory in January 2003 in California marked the company's first expansion. "We believe the number of people who want this technology is greater than those who have access to it," said Keith L. Blauer, the company's clinical director. This is not only a seemingly effective way to select a child's gender. It also brings a host of ethical (伦理的) and practical considerations—especially for the majority of families who use the technique for nonmedical reasons. The clinic offers sex selection for two purposes: to help couples avoid passing on a sex-linked genetic disease and to allow those who already have a child to "balance" their family by having a baby of the opposite sex. Blauer said the company has had an impressive success rate: 91 per cent of the women who become pregnant after sorting for a girl are successful, while 76 per cent who sort for a boy and get pregnant are successful. The technique separates sperm based on the fact that the X chromosome is larger than the Y chromosome. A machine is used to distinguish the size differences and sort the sperm accordingly.

单选题A nocturnal(夜间活动的)moth has become the first animal known to see colours in the dead of night. The moth uses this visual talent to find yellow, nectar-packed flowers in the dark, but the finding suggests that other, species also use colour vision at night. Nocturnal moths were thought to find flowers by looking for bright petals against a darker, leafy background. This difference in brightness explains why a yellow flower stands out from green leaves on a black and white photo. To test this idea, researchers at Lund University in Sweden trained nocturnal elephant hawkmoths(豆天蛾)to pick out yellow or blue artificial flowers from eight other flowers of varying shades of grey. They then made moths perform the trick in conditions as dark as a starry but moonless night. The researchers expected the moths to do badly, but to their surprise the insects picked the correct flower 90 per cent of the time. But the moths could not distinguish between lighter and darker shades of a coloured flower, even though they could still tell both from grey. "This tells us it's not a brightness-related cue,” says Almut Kelber, the sensory biologist leading the Lund team. "They could only have used the spectral(光谱的)composition of the signals—which we call colour." The moths use three separate colour receptors: blue, green and ultraviolet. At night, that leaves so little light per receptor that the insects should be almost blind. But hawkmoths have a host of adaptations to compensate. One is a mirror-like structure at the base of the eye, which reflects the light across the photoreceptors for a second time. The structure of the compound eye also allows each facet to supplement the light that strikes it with light from as many as 600 others. Kelber suspects that many other insects, and some higher animals, also use colour vision at night. She plans to look for the ability in nocturnal frogs and toads that use colour to choose their mate. "Why not? she asks. "At night there are just as many colours as during the day./

单选题Admirers of American ballet (has claimed) that (its stars) can dance (as well as) or even better than (the best of) the Russian artists.

单选题A: The wind will probably get up later. B: ______