六级经典阅读2
36. From what the Brazilian biologist says， we know that tourists like her______.
A） are reluctant to carry cash with them
B） simply don't care how much they spend
C） are not good at planning their expenditure
D）often spend more money than they can afford
37. The reason why 1994 was exceptional is that______
A）it saw an unusually large number of tourists to the U.S.
B）it witnessed a drop in the number of tourists to the U.S.
C） tourism was hardly affected by the weakening of the U.S. dollar that year
D） tourists came to the U.S. for sightseeing rather than for bargains that year
38. By saying “nobody undersells America” （Line 4，Para.3）， the author means that ______.
A） no other country underestimates the competitiveness of American products
B） no body expects the Americans to cut the prices of their commodities
C） nobody restrains the selling of American goods
D）no other country sells at a lower price that America
39. Why does the author assert that all things American are fascinating to foreigners？
A） Because they have gained much publicity through the American media.
B） Because they represent the world's latest fashions.
C） Because they embody the most sophisticated technology.
D） Because they are available at all tourist destinations.
40. From the passage we can conclude that the U.S. has come to realize
A）the weakening if the U.S. dollar can result in trade deficits
B）the lower the retail prices， the greater the profits
C）tourism can make great contributions to its economy
D）visitors to the U.S. are wealthier than U.S. tourists abroad
Passage 4
We sometimes think humans are uniquely vulnerable to anxiety， but stress seems to affect the immune defenses of lower animals too. In one experiment， for example， behavioral immunologist Mark Laudenslager， at the University of Denver， gave mild electric shocks to 24 rats. Half the animals could switch off the current by turning a wheel in their enclosure， while the other half could not. The rats in the two groups were paired so that each time one rat turned the wheel it protected both itself and its helpless partner form the shock. Laudenslager found that the immune response was depressed below normal in the helpless rats but not in those that could turn off the electricity. What he has demonstrated， he believes， is that lack of control over an event， not the experience itself， is what weakens the immune system.
Other researchers agree Jay Weiss， a psychologist at Duke University School of Medicine， has shown that animals who are allowed to control unpleasant stimuli don't develop sleep disturbances or changes in brain chemistry typical of Stressed rats. But if the animals are confronted with situations they have no control over， they later behave passively when faced with experiences they can control. Such findings reinforce psychologists' suspicions that the experience or perception of helplessness is one of the most harmful factors in depression.
One of the most startling examples of how the mind can alter the immune response was discovered by chance. In 1975 psychologist Robert Ader at the University of Rochester School of Medicine conditioned mice to avoid saccharin by simultaneously feeding them the sweetener and injecting them with a drug that while suppressing their immune systems caused stomach upsets. Associating the saccharin with the Stomach pains， the mice quickly learned to avoid the sweetener. In order to extinguish this dislike for the sweetener， Ader re-exposed the animals to saccharin. This time without the drug， and was astonished to find that those mice that had received the highest amounts of sweetener during their earlier conditioning died. He could only speculate that he had so successfully conditioned the rats that saccharin alone now served to weaken their immune systems enough to kill them.
11.Laudenslager's experiment showed that the immune system of those rats who could turn off the electricity ______ .
A） was strengthened
B） was not affected
C） was altered
D）was weakened
l2.According to the passage， the experience of helplessness causes rats to_________ .
A） try to control unpleasant stimuli
B） turn off the electricity
C） behave passively in controllable