kuaijizu

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 concentration 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.
答案为B。本题的难点在于看懂并理解文章前三句话所表达的意思。D选项包含some，在加强题中不太可能正确。

kuaijizu

For most people, the left half of the brain controls linguistic capabilities, but some people have their language centers in the right half. When a language center of the brains is damaged, for example, by a stroke, linguistic capabilities are impaired in some way. Therefore, people who have suffered a serious stroke on the left side of the brain without suffering any such impairment must have their language centers in the right half.
Which of the following is an assumption on which the reasoning in the argument above depends?
A.        No part of a person’s brain that is damaged by a stroke never recovers
B.        Impairment of linguistic capabilities does not occur in people who have not suffered any damage to any language center of the brain.
C.        Strokes tend to impair linguistic capabilities more severely than does any other cause of damage to language centers in the brain.
D.        If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages at least one of them.
E.        It is impossible to determine which side of the brain contains a person’s language centers if the person has not suffered damage to either side of the brain.
答案为D。D选项说的是左侧大脑受伤的人，故与原文结论一致；B选项说的是大脑没受伤的人，故与原文结论无关。

kuaijizu

In a study conducted in Pennsylvania, servers in various restaurants wrote “Thank you” on randomly selected bills before presenting the bills to their customers.  Tips on these bills were an average of three percentage points higher than tips on bills without the message.  Therefore, if servers in Pennsylvania regularly wrote “Thank you” on restaurant bills, their average income from tips would be significantly higher than it otherwise would have been.
Which of the following is an assumption on which the argument relies?
A.        The “Thank you” messages would have the same impact on regular patrons of a restaurant as they would on occasional patrons of the same restaurant.
B.        Regularly seeing “Thank you” written on their bills would not lead restaurant patrons to revert to their earlier tipping habits.
C.        The written “Thank you” reminds restaurant patrons that tips constitute a significant part of the income of many food servers.
D.        The rate at which people tip food servers in Pennsylvania does not vary with how expensive a restaurant is.
E.        Virtually all patrons of the Pennsylvania restaurants in the study who were given a bill with “Thank you” written on it left a larger tip than they otherwise would have.
答案为B。A项为干扰项。GMAC经常把这种貌似正确的干扰项放在正确选项之前，你在做题时一定要小心，别大意。