单选题Watching me pulling the calf awkwardly to the barn, the Irish milkmaid fought hard to Uhold back/U her laughter.

单选题He merely meant to give his opinion, not to start an argument.

单选题It was an allusion to what the scientist thought was an inappropriate distribution o funds for stem cell research.

单选题The Constitution stipulates that every citizen has the sacred obligation to defend his country.

单选题If those "mad moments"--when you can't remember what your friend has told you or where you left your keys--are becoming more frequent, mental exercises and a healthy brain diet may help. Just as bodies require more maintenance with the passing years, so do brains, which scientists now know show signs of aging as early as the 20s and 30s. "Brain aging starts at a very young age, younger than any of us had imagined and these processes continue gradually over the years," said Dr. Gary Small, the director of the Center on Aging at the University of California, Los Angeles. 'Tin convinced that it is never too early to get started on a mental or brain-fitness program," he added. In his book, The Memory Bible, the 51-year-old neuroscientist (神经学家) lists what he refers to as the 10 suggestions for keeping the brain young. They include training memory, building skills, reducing stress, mental exercises, brain food and a healthy lifestyle. "Misplacing your keys a couple of times don't mean you should start labeling your cabinets. Memory loss is not an inevitable consequence of aging. Our brains can fight back," he said. Small provides the weapons for a full-scale attack. Simple memory tests give an indication of what you are up against and tools such as "look" and "connect" are designed to make sure that important things such as names and dates are never forgotten. "So if you wanted to learn names and faces, for example, you meet Mrs. Beatty and you notice a distinguishing facial feature, maybe a high eyebrow," said Small. "You associate the first thing that comes to your mind. I think of the actor Warren Beatty, so I create a mental picture of Warren Beatty kissing her brow." Small admits it may sound a bit strange but he says it works. "Mental exercises could be anything from doing crossword puzzles and writing with your left hand if you are right handed or learning a language. It could be anything that is fun that people enjoy doing," he added.

单选题The author quotes the example of our ancestors to show that education emerged ______

单选题Difficulties and hardships have ______ the best qualities of the young geologist.

单选题A: I don't know why we listen to George? B: ______.

单选题Birds are literally half-asleep-with one brain hemisphere alert and the other sleeping, according to a new study of sleeping ducks. Earlier studies have documented half-brain sleep in a wide range of birds. The brain hemispheres take turns sinking into the sleep stage characterized by slow brain waves. The eye controlled by the sleeping hemisphere keeps shut, while the wakeful hemisphere's eye stays open and alert. Birds also can sleep with both hemispheres resting at once. Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end-of-the-row sleepers. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction. Also, birds dozing (打盹) at the end of the line resorted to single-hemisphere sleep, rather than total relaxation, more often than inner ducks did. Rotating 16 birds through the positions in a four-duck row, the researchers found outer birds half-asleep during 32 percent of dozing time versus about 12 percent for birds in internal spots. "We believe this is the first evidence for an animal behaviorally controlling sleep and wakefulness simultaneously in different regions of the brain," the researchers say. The results provide the best evidence for a long-standing supposition that single- hemisphere sleep evolved as creatures scanned for enemies. The preference for opening an eye on the lockout side could be widespread, he predicts. He's seen it in a pair of birds' dozing side-by-side in the zoo and in a single pet bird sleeping by a mirror. The mirror-side eye closed as if the reflection were a companion and the other eye stayed open. Useful as half-sleeping might be, it's only been found in birds and such water mammals(哺乳动物) as dolphins, whales, and seals. Perhaps keeping one side of the brain awake allows a sleeping animal to surface occasionally to avoid drowning. Studies of birds may offer Unique insights into sleep. Jerome M. Siegel of the UCLA says he wonders if birds' half-brain sleep "is just the tip of the iceberg (冰山) ". He speculates that more examples may turn up when we take a closer look at other species.

单选题We sometimes think humans are uniquely vulnerable to anxiety, but stress seems to affect the immune defenses of lower animals too. In one experiment, for example, behavioral immunologist ( 免疫学家) Mark Laudenslager, at the University of Denver, gave mild electric shocks to 24 rats. Half the animals could switch off the current by turning a wheel in their enclosure, while the other half could not. The rats in the two groups were paired so that each time one rat turned the wheel it protected both itself and its helpless partner from the shock. Laudenslager found that the immune response was depressed below normal in the helpless rats but not in those that could turn off the electricity. What he has demonstrated, he believes, is that lack of control over an event, not the experience itself, is what wakens the immune system. Other researchers agree. Jay Weiss, a psychologist at Duke University School of Medicine, has shown that animals who are allowed to control unpleasant stimuli don't develop sleep disturbances or changes in brain chemistry typical of stressed rats. But if the animals are conditioned to confront with situations they have no control over, they later behave passively even when faced with experiences they can control. Such findings reinforce psychologists' suspicions that the experience or perception of helplessness is one of the most harmful factors in depression. One of the most startling examples of how the mind can alter the immune response was discovered by chance. In 1975 psychologist Robert Ader at the University of Rochester School of Medicine conditioned (使形成条件反射) mice to avoid saccharin (糖精) by simultaneously feeding them the sweetener and injecting them with a drug that while suppressing their immune systems caused stomach upsets. Associating the saccharin with the stomach pains, the mice quickly learned to avoid the sweetener. In order to extinguish this dislike for the sweetener, Ader reexposed the animals to saccharin, this time without the drug, and was astonished to find that those mice that had received the highest amounts of sweetener during their earlier conditioning died. He could only speculate that he had so successfully conditioned the rats that saccharin alone now served to weaken their immune systems enough to kill them.

单选题The fierce looking horse is in fact very tame and you can set your mind at ease when you ride it.

单选题Pollutants introduced into a lake can rapidly accelerate its natural aging process.

单选题The State Council will lay down new rules that aim to make management compatible with internationally accepted {{U}}conventions{{/U}}.

单选题Scientists are______certain that there is a cancer-inhibiting agent in the blood of the shark.

单选题A: ______ B: My head aches and I've got a sore throat, too.

单选题Bret Harte, (which) best-known works describe life in California in the mid-1800's, (helped shape) the (literary) movement (called) local-color writing.

单选题So long as teachers fail to distinguish between teaching and learning, they will continue to undertake to do for children that which only children can do for themselves. Teaching children to read is not passing reading on to them. It is certainly not endless hours spent in activities about reading. Douglas insists that "reading cannot be taught directly and schools should stop trying to do the impossible. " Teaching and learning are two entirely different processes. They differ in kind and function. The function of teaching is to create the conditions and the climate that will make it possible for children to devise the most efficient system for teaching themselves to read. Teaching is also a public activity: It can be seen and observed. Learning to read involves all that each individual does to make sense of the world of printed language. Almost all of it is private, for learning is an occupation of the mind, and that process is not open to public scrutiny. If teacher and learner roles are not interchangeable, what then can be done through teaching that will aid the child in the quest (探索) for knowledge? Smith has one principal rule for all teaching instructions. "Make learning to read easy, which means making reading a meaningful, enjoyable and frequent experience for children. " When the roles of teacher and learner are seen for what they are, and when both teacher and learner fulfill them appropriately, then much of the pressure and feeling of failure for both is eliminated. Learning to read is made easier when teachers create an environment where children are given the opportunity to solve the problem of learning to read by reading.

单选题According to a prominent philosopher, intolerance is a ______ to understanding.

单选题{{B}}Passage Three{{/B}} Most people think of lions as strictly African beasts, but only because they're been killed off almost everywhere else. Ten thousand years ago lions spanned vast sections of the globe. Now lions hold only a small fraction of their former habitat, and Asiatic lions, a subspecies that split from African lions perhaps 100,000 years ago, hang on to an almost impossibly small slice of their former territory. India is the proud steward of these 300 or so lions, which live primarily in a 560-square-mile sanctuary (保护区). It took me a year and a half to get a permit to explore the entire Gir Forest--and no time at all to see why these lions became symbols of royalty and greatness. A tiger will hide in the forest unseen, but a lion stands its ground, curious and unafraid--lionhearted. Though they told me in subtle ways when I got too close, Gir’s lions allowed me unique glimpses into their lives during my three months in the forest. It's odd to think that they are threatened by extinction; Gir has as many lions as it can hold--too many, in fact. With territory in short supply, lions move about near the boundary of the forest and even leave it altogether, often clashing with people. That's one reason India is creating a second sanctuary. There are other pressing reasons: outbreaks of disease or natural disasters. In 1994 a serious disease killed more than a third of Africa's Serengeti lions--a thousand animals--a fate that could easily happen to Gir's cats. These lions are especially vulnerable to disease because they descend from as few as a dozen individuals. "If you do a DNA test, Asiatic lions actually look like identical twins," says Stephen O'Brien, a geneticist (基因学家) who has studied them. Yet the dangers are hidden, and you wouldn't suspect them by watching these lords of the forest. The lions display vitality, and no small measure of charm. Though the gentle intimacy of play vanishes when it's time to eat, meals in Gir are not necessarily frantic affairs. For a mother and her baby lion sharing a deer, or a young male eating an antelope (羚羊), there's no need to fight for a cut of the kill. The animals they hunt for food are generally smaller in Gir than those in Africa, and hunting groups tend to be smaller as well.

单选题The Taoist believe that the senses are doors through which the freed soul rushes to Umingle/U with the colors and tones of the universe.