GWD-25-36

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.

Answer: B  不理解, 给点思路吧

在人清醒的时候,Adenosine 会和人脑某个区间中越来越多的细胞bind; 人入睡之后,binging会减少. researchers 于是推测, binding 的累积是onset of sleep的原因.

C 说,Caffeine可以通过阻碍binding 使人保持清醒, 所以反向支持了假想.

可以吗?

同意楼上的，B应该就是阻碍了bingding.