1.        GWD-25-Q36

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?

A.      Even after long periods of sleep when adenosine is at its lowest concen-

tration in the brain, the number of brain cells bound with adenosine remains

very large.

B.       Caffeine, which has the effect of making people remain wakeful, is known to

interfere with the binding of adenosine to sites on brain cells.

C.      Besides binding to sites in the brain, adenosine is known to be involved in

biochemical reactions throughout the body.

D.      Some areas of the brain that are relatively inactive nonetheless release

some adenosine.

E.       Stress resulting from a dangerous situation can preserve wakefulness even

when brain levels of bound adenosine are high.

江湖上的朋友们，帮忙看看这个为啥选B了

Researchers的假设: chemical A在醒着时, 会一直增加…增加到最大就会启动睡眠

找SUPPORT

选项B
咖啡因能让人保持清醒，妨碍了A去bind to sites，也就妨碍了睡眠，支持了结论A bind to 细胞上的sites到一定数量导致了睡眠。

请指教