单选题A: Sorry to bother you, but could you tell me the way to the Sunset Road?B: ______

单选题He wanted to stay at home, but at last he agreed, very ______ though, to go to the concert.

单选题A: Why were only three of you present at the meeting? B: ______.

单选题(Thirteen hundred) medical professionals, (all of which) have been trained to treat drug dependency, (attended) the annual convention (sponsored) by a society.

单选题The principal duty of the United Nations is to safeguard the peace of the world.

单选题Mrs. Brown couldn't shake the ______ that these kids were in deep trouble and it was up to her to help them.

单选题The government has called for an independent Uinquiry/U into the incident.

单选题All of the following are true of Comment 3 EXCEPT that_______ 。

单选题Thousands of civilians in the country were massacred in the air boming.

单选题I couldn't Uwork out/U why anyone would invent something so boring.

单选题The prehistoric art of inscribing figures and designs on rock surfaces seems to have slowly disappeared with the advent of agriculture, which required a large amount of time and energy.

单选题The peahen is {{U}}a bit{{/U}} smaller than the peacock and does not have a long, colorful tail.

单选题The fireman had a ______ escape when a staircase collapsed beneath this feet.

单选题{{B}}Passage Four{{/B}} 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 (免疫学家) 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 from 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 wakens 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 conditioned to confront with situations they have no control over, they later behave passively even 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 (便形成条件反射) mice to avoid saccharin (糖精) 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 reexposed 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.

单选题You have to finish the work within the ______ time.

单选题A compound break is more serious than a simple one because there is more opportunity for loss of blood and infection.

单选题(Breaking) up water (into) hydrogen and oxygen is a good example of (as) is known as (a chemical change).

单选题(That) the woman (was saying) was so important that I asked everyone (to stop) talking and (listen).