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题库 / GMATLA-CR-88
The chemical adenosine is released by brain cells when those cells are active. Adenosine then binds to more and more sites on cells in certain areas of the brain, as the total amount released gradually increases during wakefulness. During sleep, the number of sites to which adenosine is bound decreases. Some researchers have hypothesized that it is the cumulative binding of adenosine to a large number of sites that causes the onset of sleep.
Which of the following, if true, provides the most support for the researchers' hypothesis?
Even after long periods of sleep when adenosine is at its lowest concentration in the brain, the number of brain cells bound with adenosine remains very large.
Caffeine, which has the effect of making people remain wakeful, is known to interfere with the binding of adenosine to sites on brain cells.
Besides binding to sites in the brain, adenosine is known to be involved in biochemical reactions throughout the body.
Some areas of the brain that are relatively inactive nonetheless release some adenosine.
Stress resulting from a dangerous situation can preserve wakefulness even when brain levels of bound adenosine are high.
科学家预言，连续的A物质绑定大量接收器导致了睡眠的开始。
A 讲的是睡了很长一段时间，与原题不符。
B 咖啡因影响A物质与大脑的接收器的绑定，导致清醒。正确。
以下为无关选项。
C A物质的性质。
D 脑的其他区域。
E 压力的影响。
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