单选题Hitchhiking (搭车旅游) When I was in my teens (十几岁) and 20s, hitchhiking was a main form of long-distance transport. The kindness or curiosity of strangers 1 me all over Europe, North America, Asia and southern Africa. Some of the lift-givers became friends, many provided hospitality 2 the road. Not only did you find out much more about a country than 3 traveling by train or plane, but also there was that element of excitement about where you would finish up that night. Hitchhiking featured importantly in Western culture. It has books and songs about it. So what has happened to 4 ? A few years ago, I asked the same question about hitchhiking in a column on a newspaper. 5 of people from all over the world responded with their view on the state of hitchhiking. "If there is a hitchhiker"s 6 it must be Iran," came one reply. Rural Ireland was recommended as a friendly place for hitchhiking, 7 was Quebec, Canada—"if you don"t mind being berated (严厉指责) for not speaking French." But while hitchhiking was clearly still alive and well in many parts of the world, the 8 feeling was that throughout much of the west it was doomed (消亡). With so much news about crime in the media, people assumed that anyone on the open road without the money for even a bus ticket must present a danger. But do we 9 to be so wary both to hitchhike and to give a lift? In Poland in the 1960s, 10 a Polish woman who e-mailed me, "the authorities introduced the Hitchhiker" Booklet. The booklet contained coupons for drivers, so each time a driver 11 somebody, he or she received a coupon. At the end of the season, 12 who had picked up the most hikers were rewarded with various prizes. Everybody was hitchhiking then." Surely this is a good idea for society. Hitchhiking would increase respect by breaking down 13 between strangers. It would help fight 14 warming by cutting down on fuel consumption as hitchhikers would be using existing fuels. It would also improve educational standards by delivering instant 15 in geography, history, politics and sociology.

单选题When snow collects on top of a building during the winter, the weight sometimes weakens the construction and occasionally causes the roof to collapse. A. selects B. scatters C. melts D. accumulates

单选题The second injection should have been given once the first drug had {{U}}taken effect{{/U}}.

单选题I Urarely/U wear a raincoat because I spend most of my time in a car.

单选题It is the movement, not the color, of objects that excites the bull.

单选题Nothing would induce me to vote for him again.

单选题He doesn't like the children who are prone to telling a lie.A. reliableB. liableC. promisingD. declined

单选题The two girls look Ualike/U.

单选题We have to ask them to quit talking in order that all people present could hear us clearly.A. decreaseB. ceaseC. continueD. keep

单选题Can you give me a concrete example to support your idea?A. specialB. goodC. realD. specific

单选题Did anyone call when I was out? A. everyone C. nobody B. someone D. anybody

单选题When the car accident happened, we were all horrified. A. take out B. take place C. take in D. take away

单选题You look smart in the new suit.

单选题John removed his overcoat.

单选题When We Are Asleep Everyone dreams, but some people never recall their dreams, or do so very rarely. Other people always wake up with vivid recollections (记忆) of their dreams, though they forget them very quickly. In an average night of eight hours" sleep, an average adult will dream for around one hundred minutes, probably having three to five dreams, each lasting from ten to thirty minutes. Scientists can detect when someone is having a dream by using an instrument which measures the electrical waves in the brain. During dreaming, these waves move more quickly. Breathing and pulse rate also increase, and there are rapid eye movements under the lids, just as though the dreamer were really looking at moving objects. These signs of dreaming have been detected in all mammals (哺乳动物) studied, including dogs, monkeys, cats, and elephants, and also some birds and reptiles (爬行动物). This period of sleep is called the "D" state for around 50% of their sleep; the period reduces to around 25% by the age of 10. Dreams take the form of stories, but they may be strange and with incidents not connected, which make little sense. Dreams are seldom without people in them and they are usually about people we know. One estimate says that two-thirds of the "cast" of our dream dramas are friends and relations. Vision seems an essential part of dreams, except for people blind from birth. Sound and touch are senses also often aroused, but smell and taste are not frequently involved. In "normal" dreams, the dreamer may be taking part, or be only an observer. But he or she cannot control what happens in the dream. However, the dreamer does have control over one type of dream. This type of dream is called a "lucid" (清醒的) dream. Not everyone is a lucid dreamer. Some people are occasional lucid dreamers. Others can dream lucidly more or less all the time. In a lucid dream, the dreamer knows that he is dreaming.

单选题 Alpha Particle From decaying radon (氡) atoms can destroy the living cells they strike and increase the likelihood that those cells will later become cancerous. Researchers have now directly demonstrated that neighboring cells not suffering direct hits can be harmed, too. They've also taken a step toward showing how this type of radiation, called alpha particles, indirectly hurts those bystanders. Radon derives from the decay of uranium (铀) and seeps naturally into the air from the ground. It's the primary environmental source of alpha particles, which contribute to cancer risk by causing aberrations (失常) in DNA. Alpha particles from inhaled radon are second only to smoking as a cause of lung cancer. Because a person's exposure to alpha particles typically is low, researchers have had to estimate public health threats from radon by guess from the effects of higher doses of alpha radiation. Such data comes primarily from studies of survivors of the atomic bombs that destroyed Hiroshima and Nagasaki in Japan. The customary extrapolation (推测) assumes that cancer risk is proportional to the dose of radiation even at low doses. Radiation's effects in cell structure don't necessarily reflect what happens in "a whole organism, with its full range of defense repair mechanisms," says Duport. Processes such as DNA repair and cell death triggered by radiation damage could cancel the effect on by stander cells observed in the lab, he suggests. Furthermore, while a bystander effect can contribute to cancer, other cell-to-cell interactions in living tissue "may relieve increased risk." says Barry Michael, a radiation biophysicist at the Gray Cancer Institute in Northwood, England. One of these interactions halts cell division and hence cancer. "The jury is still out on whether cell-to-cell effects lead to a greater or lower risk," Michael says.

单选题Sleep Necessary for Memories Burning the midnight oil before an exam or interview does harm to the performance according to a recent research which found that sleep is necessary for memories to be taken back into the brain. A good night"s sleep within 30 hours of trying to remember a new task is a required condition of having good recall in the weeks ahead, scientists have found. The research, published in the December issue of Nature Neuroscience , showed that it was the act of sleep, rather than the simple passage of time, that was critical for long-term memory formation. "We think that getting that first night"s sleep starts the process of memory consolidation (巩固)," said Robert Stickgold, a sleep researcher at Harvard Medical School who conducted the latest study. "It seems that memories normally wash out of the brain unless some process nails them down. My suspicion is that sleep is one of those things that does the nailing down," Professor Stickgold said. With about one in five people claiming that they are so chronically short of sleep that it affects their daily activities, the latest work emphasizes the less well--understood side effect—serious memory impairment (损害). Volunteers in an experiment found it easier to remember a memory task if they were allowed to sleep that night. But for those kept awake, no amount of subsequent sleep made up for the initial loss. Professor Stickgold"s team trained 24 people to identify the direction of three diagonal (斜线形的) bars flashed for a sixtieth of a second on a computer screen full of horizontal (水平的) stripes. Half of the subjects were kept awake that night, while the others slept. Both groups were allowed to sleep for the second and third nights to make up for any differences in tiredness between the volunteers. Those who slept the first night were significantly and consistently better at remembering the task while the second group showed no improvement despite enjoying two nights of catch-up sleep.

单选题If the test taker finds an item to which an answer is not known, it may be wise to leave it blank and go on with the test. A. valuable B. advisable C. considerable D. probable

单选题Although he was under no Uobligation/U the shopkeeper replaced the defective battery free of charge.

单选题John is crazy about pop music.A. sorryB. madC. concernedD. worried