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.

答案是B，我怎么想不清楚题目里的关系总觉得B是反的。哪位NN能给我一条推理链啊！大谢！！！

cumulative binding of adenosine to a large number of sites  ----- 〉the onset of sleep

A. focused on the number of brain cells bound with adenosine, an irrelavant explananation.

B. shed light on the reasoning that wakefulness, the opposite to sleepness, will maintain if the binding of adenosine is inhibited. A proper support namely "no cause, then no result".

Besides, whether biochemical reaction involved itself as C says, which part of brain involving adenosine release in D and what happended while brain level of bound adenosine are all irrelevant answers.

哦，那题目的意思就是说

醒着，绑在sites上的a越来越多，人就慢慢困了，想睡觉了？是这个意思吧？