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: ______

单选题A: Front desk. Can I help you? B: ______

单选题While living in Brazil, I used to {{U}}crave{{/U}} the dishes prepared by my mother.

单选题The states had no recourse but to look forward to the verdict of the high tribunal.

单选题Whether a gun is a weapon of offence or a weapon of ______ depends on which end of it you are at.

单选题The fridge is considered a necessity. It has been so since the 1960s when packaged food first appeared with the label: "store in the refrigerator. " In my fridgeless fifties childhood, I was fed well and healthily. The milkman came daily, the grocer, the butcher, the baker, and the ice-cream man delivered two or three times a week. The Sunday meat would last until Wednesday and surplus bread and milk became all kinds of cakes. Nothing was wasted, and we were never troubled by rotten food. Thirty years on food deliveries have ceased, fresh vegetables are almost unobtainable in the country. The invention of the fridge contributed comparatively little to the art of food preservation. A vast way of well-tried techniques already existed—natural cooling, drying, smoking salting, sugaring, bottling... What refrigeration did promote was marketing—marketing hardware and electricity, marketing soft drinks, marketing dead bodies of animals around the globe in search of a good price. Consequently, most of the world's fridges are to be found, not in the tropics where they might prove useful, but in the wealthy countries with mild temperatures where they are climatically almost unnecessary. Every winter, millions of fridges hum away continuously, and at vast expense, busily maintaining an artificially-cooled space inside an artificially-heated house while outside, nature provides the desired temperature free of charge. The fridge's effect upon the environment has been evident, while its contribution to human happiness has been insignificant. If you don't believe me, try it yourself, invest in a food cabinet and turn off your fridge next winter. You may miss the hamburgers, but at least you'll get rid of that terrible hum.

单选题Man: Sam has bought a laptop. I felt I should buy one too. Woman.. How can you hold a candle to him? What does his father do, do you know? Question: What does the woman mean?

单选题(Despite) the growth of (manufacturing) and other industries, the economy of the state of Texas (has) remained heavily (dependence) on oil and gas.

单选题A: This pain in my head is terrible. B: ______