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  3. (1)Dinges is one of the few women in the Army certified at level 2 combat. Level 2 involves a lot of training with two attackers

(1)Dinges is one of the few women in the Army certified at level 2 combat. Level 2 involves a lot of training with two attackers

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问题     (1)Dinges is one of the few women in the Army certified at level 2 combat. Level 2 involves a lot of training with two attackers on one, she explains, with the hope of "you being the one guy getting out alive." In the years ahead,Dinges may face an even harder fight. She belongs to a family carrying the gene for fatal familial insomnia. The main symptom of FFI, as the disease is often called, is the inability to sleep. First the ability to nap disappears, then the ability to get a full night’s sleep, until the patient cannot sleep at all. The syndrome usually strikes when the sufferer is in his or her 50s, ordinarily lasts about a year, and, as the name indicates, always ends in death.
    (2)FFI is an awful disease, made even worse by the fact that we know so little about how it works. After years of study, researchers have figured out that in a patient with FFI, malformed proteins called prions attack the sufferer’s thalamus, a structure deep in the brain, and that a damaged thalamus interferes with sleep. But they don’t know why this happens, or how to stop it, or ease its brutal symptoms. Before FFI was investigated, most researchers didn’t even know the thalamus had anything to do with sleep. FFI is exceedingly rare, known in only 40 families worldwide. But in one respect, it’s a lot like the less serious kinds of insomnia(失眠症)plaguing millions of people today: It’s pretty much a mystery.
    (3)If we don’t know why we can’t sleep, it’s in part because we don’t really know why we need to sleep in the first place. We know we miss it if we don’t have it. And we know that no matter how much we try to resist it, sleep conquers us in the end. We know that seven to nine hours after giving in to sleep, most of us are ready to get up again, and 15 to 17 hours after that we are tired once more. We have known for 50 years that we divide our sleep between periods of deep-wave sleep and what is called rapid eye movement(REM)sleep, when the brain is as active as when we’re awake, but our voluntary muscles are paralyzed. We know that all mammals and birds sleep. A dolphin sleeps with half its brain awake so it can remain aware of its underwater environment. When wild ducks sleep in a line, the two outermost birds are able to keep half of their brains alert and one eye open to guard against predators. Fish, reptiles, and insects all experience some kind of repose too.
    (4)The predominant theory of sleep is that the brain demands it. This idea derives in part from common sense—whose head doesn’t feel clearer after a good night’s sleep? But the trick is to confirm this assumption with real data. How does sleeping help the brain? The answer may depend on what kind of sleep you are talking about. Recently, researchers at Harvard led by Robert Stickgold tested undergraduates on various aptitude tests, allowed them to nap, then tested them again. They found that those who had engaged in REM sleep subsequently performed better in pattern recognition tasks, such as grammar, while those who slept deeply were better at memorization. Other researchers have found that the sleeping brain appears to repeat a pattern of neuron firing that occurred while the subject was recently awake, as if in sleep the brain were trying to commit to long-term memory what it had learned that day.
    (5)Such studies suggest that memory consolidation may be one function of sleep. Giulio Tononi, a noted sleep researcher at the University of Wisconsin, Madison, published an interesting twist on this theory a few years ago: His study showed that the sleeping brain seems to weed out redundant or unnecessary connections. So the purpose of sleep may be to help us remember what’s important, by letting us forget what’s not.
    (6)Sleep is likely to have physiological purposes too: That patients with FFI never live long is likely significant. A lot of interest has focused on what exactly kills them, but we still don’t know. Do they literally die from lack of sleep? And if not, to what extent does sleeplessness contribute to the conditions that kill them? Some researchers have found that sleep deprivation impedes wound healing in rats, and others have suggested that sleep helps boost the immune system and control infection. But these studies are not conclusive.
    (7)In the most famous attempt to figure out why we sleep, in the 1980s, Rechtschaffen forced rats to stay awake in his University of Chicago lab by placing mem on a disk suspended on a spindle over a tank of water. If the rats fell asleep, the disk would turn and throw them in the water; when they fell into the water, they immediately woke up. After about two weeks of this strict enforcement of sleeplessness, all the rats were dead. But when Rechtschaffen performed necropsies on the animals, he could not find anything significantly wrong with them. Their organs were not damaged; they appeared to have died from exhaustion—that is, from not sleeping. A follow-up experiment in 2002, with more sophisticated instruments, again failed to find "an unambiguous cause of death" in the rats. At Stanford University I visited William Dement, the retired dean of sleep studies, a co-discoverer of REM sleep, and co-founder of the Stanford Sleep Medicine Center. I asked him to tell me what he knew, after 50 years of research, about the reason we sleep. "As far as I know," he answered, "the only reason we need to sleep that is really, really solid is because we get sleepy."
The third paragraph of the passage serves to _____.
选项 A、explain why people and animals need sleep
B、summarize the functions of sleep
C、summarize what people have known about sleep
D、describe what harm is brought about by lack of sleep
答案C
解析 第3段介绍了目前研究已发现的有关睡眠的一些事实，因此本题选C。该段第1句指出“我们其实不明白为什么我们需要睡眠”，A与此不符；B所说的睡眠的功能是第4—6段阐述的内容；D所说的缺乏睡眠的坏处则是在第6段提到。
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