The more hours that young children spend in child care, the more likely they are to turn out aggressive and disobedient by the time they are in kindergarten, according to the largest study of child care and development ever conducted. Researchers said this correlation (相关性) held true regardless of whether the children came from rich or poor homes, were looked after by a relative or at a center, and whether they were girls or boys.

    What is uncertain, however, is whether the child care actually causes the problem or whether children likely to turn out aggressive happen to be those who spend more hours in child care. It also remains unclear whether reducing the amount of time in child care will reduce the risk that a child will turn into a mean person. What's more, quality child care is associated with increased skills in intellectual ability such as language and memory, leading some academics to suggest that child care turns out children who are “smart and naughty”.

    The government-sponsored research, which has tracked more than 1,300 children at 10 sites across the country since 1991, is bound to cause the debate over child care again: How should people balance work and family? And how should parents, especially mothers. Resolve the demands that are placed on them to be both breadwinners and supermoms?

    That debate was already on display at a news briefing yesterday, where researchers themselves had different opinions about the data and its implications (含义). “There is a constant relationship between time in care and problem behavior, especially those involving aggression and behavior,” said Jay Belsky of Birkbeck College in London, one of the lead investigators of the study who has previously annoyed women's groups because of his criticisms of child care. “On behalf of fathers or mothers?” interrupted Sarah Friedman, a developmental psychologist at the National Institute of Child Health and Human Development (NICHD) and one of the other lead scientists on the study. “On behalf of parents and families,” responded Belsky.

    “NICHD is not willing to get into policy recommendations.” said Friedman, contradicting her colleague. “There are other possibilities that can be entertained. Yes it is a quick solution—more hours in child care is associated with more problems. The easy solution is to cut the number of hours but that may have implications for the family that may not be beneficial for the development of the children in terms of economics.” In an interview after the briefing, Friedman said that asking parents to work fewer hours and spend more time with their children usually meant a loss of family income, which adversely(不利地) affects children.

    Scientists said that the study was highly reliable. But the researchers said they had no idea whether the behavioral difficulties persisted as the children moved to higher grades.

    Social change is more likely to occur in societies where there is a mixture of different kinds of people than in societies where people are similar in many ways. The simple reason for this is that there are more different ways of looking at things present in the first kind of society. There are more ideas, more disagreements in interest, and more groups and organizations with different beliefs. In addition, there is usually a greater worldly interest and greater tolerance in mixed societies. All these factors tend to promote social change by opening more areas of life to decision. In a society where people are quite similar in many ways, there are fewer occasions for people to see the need or the opportunity for change because everything seems to be the same. And although conditions may not be satisfactory, they are at least conventional and generally agreed.

    Within a society, social change is also likely to occur more frequently and more readily in the material aspects of the culture than in the non-material, for example, in technology rather than in values; in what has been learned later in life rather than what was learned early; in the less basic and less emotional aspects of society-than in their opposites; in the simple elements rather than in the complex ones; in form rather than in substance; and in elements that are acceptable to the culture rather than in strange elements.

    Furthermore, social change is easier if it is gradual. This is one reason why change has not come more quickly to Black Americans as compared to other American minorities, because of the sharp difference in appearance between them and white people.

根据短文内容，选择最佳答案，并将选定答案的字母标号填在题前括号内。

    A student was one day taking a walk with his teacher. As they went along, they saw a pair of old shoes lying in the path. They were a poor farmer's, who was working in the nearby field.

    The student turned to the teacher, saying: “we will hide his shoes, and hide ourselves behind those trees, and wait to see what he will do.”

    “My young friend,” answered the teacher, “we should never make fun of the poor. Why not put a coin in each shoe, and then we will hide ourselves and watch?” The student did so and they both hid themselves behind the trees. The poor man soon finished his work, and came across the field to the path where he had left his coat and shoes.

    After putting on his coat, he put his foot into one of his shoes, and felt something hard. Then he bent(弯腰) down to feel what it was, and found the coin. Surprised, he looked at the coin, turned it around and looked at it again. He then looked around, but no person was seen. He put the money into his pocket, and continued to put on the other shoe. His surprise was doubled on finding the other coin.

    He couldn't control his feelings and fell to his knees, looked up to the sky and expressed his thanks. Then he spoke of his wife, sick and helpless, and his children without bread. He said the help would save them from dying.

    The student stood there deeply moved, and his eyes were filled with tears. “Now,” said the teacher, “Are you not much happier than if you had hidden the shoes?”

    Most Europeans want small cars. Many Americans prefer large cars. As a result, European automakers produce a large number of economical, light weight cars, while American automakers build bigger, heavier cars.

    The price of gas has much to do with this. The petrol is expensive in Europe, so Europeans naturally prefer cars that will go a long way on a small amount of fuel. There are other reasons. Many European cities have very narrow streets. In these cities a small car is more practical and easier to handle than a large one.

    Some Americans like powerful engines in their cars. They enjoy having wider cars that are comfortable for large families and long trips. They are prepared to pay higher costs to get these advantages. Other Americans, however, have learned to like the small and smart cars. Many visitors to Europe during and after World War I discovered that small cars were fun to drive and easy to park in small spaces. They were delighted to learn how far small cars could go on a few gallons of gasoline.

    In the 1950s many Americans began buying European cars. In 1957, for the first time, the United States imported more cars than it exported. The best seller among these imported cars was a cool-looking but small car from Germany. Americans immediately gave it another name “ the bug”.

    Today, American car buyers have a wider choice. There are big cars for people who want large room, comfort, and power. And there are small cars, mostly imported but some American-made, for people who want easy parking and economical operation.

    There is an English saying that says, "Let Sleeping Dogs Lie." It means not bringing up an old problem. Researchers in Hungary have found another reason to let dogs keep on sleeping. It seems the animals are learning while they sleep.

    The Hungarian researchers placed tools on the dogs' heads to know about electrical activity in the brain. The brain activity, called sleep spindles(梭状波), takes place in human begins, and has been connected with learning. The researchers hope to understand how the dogs' ability to learn and remember changes as they get older. The study may help them understand how human brains change as we age.

    The researchers found differences between male and female dogs. Iotchey, a researcher, says the females appeared much better at learning new things. Female dogs have about twice as many spindles per minute as male dogs, they also happen to be the better learners, and they memorize the task much better. But it was harder for all the older dogs to remember things, especially when several things were happening at the same time.

    DoraSzabo also studies sleep spindles. Szabo is a neuroscientist in a university in Budapest. She says the older dogs have fewer spindles and are easily cheated. "If you first hide the reward into one bowl, then in another and in another, they get lost after a while. So their performance is going down, and they are getting poor in solving new problems."

    Researchers hope the study will not only help understanding of learning ability and memory changes in dogs, but also the aging of humans. Senior Researcher EnikoKubinyi adds that the aging dogs suffer from the same problems as humans who are aging. “Among very old dogs, up to two thirds of them show signs of dementia(痴呆), and this dementia is really very similar to that of humans, so we could use dog as a natural model of human aging."

    Professional athletes pay a high price for their pursuit of excellence and glory. Training to the limit tears muscles and wears out joints. Gymnasts often need hip replacements when barely into middle age. Few footballers make it to the end of their careers with their knees intact.

    But many also run a darker risk: doping—the use of banned athletic performance-enhancing drugs by athletic competitors. The Winter Olympics in Pyeongchang, in South Korea, starts this week in its shadow. Years after whistle-blowers first revealed wholesale (大规模的) doping in Russia, the International Olympic Committee (IOC) at last decided to bar it from taking part. But it has allowed many Russians to compete as individuals. And on the eve of the competition the Court of Arbitration for Sport (CAS) said that 28 others should receive a more tolerant penalty from the IOC, further muffling the anti-doping message.

    Russia's doping is unusual only in its scale and institutional nature. No country or sport is immune. Studies, and an anonymous survey at the World Athletics Championships in 2011, suggest that a third of athletes preparing for big international competitions take banned substances. Yet just 1-2% fail a test each year. Lance Armstrong, a cyclist who won the Tour de France seven times and later admitted to doping all the while, was tested on 250 occasions. The few times he failed, he avoided punishments by claiming he had taken anti-inflammatories (消炎药) for saddle-sores (骑行引起的肌肉酸痛).

    Doping is more sophisticated than when some states used steroids (类固醇) to bulk up athletes. New drugs are designed to be undetectable in a blood or urine sample. Many athletes "blood dope," receiving transfusions or taking a drug that stimulates the production of red blood cells to improve their physical strength. Soviet athletes who were fed steroids suffered a host of serious problems in later life. They were more likely to commit suicide, or to miscarry (流产) or have a disabled child. No one knows what risks those taking new "designer" versions are running. Blood-doping can cause heart attacks; more than a dozen cyclists' deaths have already been linked to it.

    The agencies that set out to stop doping are hugely outclassed. As the argument over punishments on Russia illustrate, they are divided and weak. Most testing is done by national bodies, which may not try very hard to find evidence that would get their own stars banned. The World Anti-Doping Agency (WADA), which oversees them, is packed with officials from national sports federations and the IOC. Their interests are likewise conflicted. Its budget is tiny. The system seems to be designed to look tough but punish only the occasional scapegoat (替罪羊). Honest athletes deserve better.