单选题 Regeneration of Limbs Most people would agree that it would be wonderful if humans could regenerate limbs. These who have lost their arms or legs would be complete again. The day is still far off when this might happen. But in the last 10 years, doctors have reported regeneration in smaller parts of the body, most often fingers. Regeneration is not a newly-discovered process. For centuries, scientists have seen it work in some kinds of animals. Break off a lizard's (蜥蜴的) tail, for example, and it will grow a new tail. Scientists now are looking for a way to turn on this exciting ability in more highly-developed animals, including humans. Their experiments show that nerves, cell chemistry and the natural electric currents in the body all seem to have a part in this process. The body of every animal contains general purpose cells that change into whatever kind of cells the body needs. Animals such as the lizard or salamander (蝾螈) use these cells to regenerate a new tail or leg when the old one is broken off. These cells collect around the wound. They form a mass called a blastama (胚基). The cells of the blastema begin to change. Some become bone cells, some muscle cells, some skin cells. Slowly, a new part regrows from the body outward. When completed, the new part is just like the old one. Mote than 200 years ago, Italian scientist Luigi Spallanzani showed that younger animals have a greater ability to regenerate lost parts than older animals. So do animals lower on the ladder of evolutionary development. The major difference seems to be that less-developed animals have more nerves in their tails and legs than humans do in their arms and legs. Another helpful piece of information was discovered in the late 1600s. Scientists found that when a creature is injured, an electrical current flows around the wound. The strength of the current depends on how severe the wound is and on how much nerve tissue is present. In 1945, American scientist Meryl Rose tested another idea about regeneration. He thought a new limb might grow only from an open wound. Doctor Rose cut off the front legs of some frogs, below the knee. He kept the wounds wet with a strong salty liquid. This prevented skin from growing over the wounds. The results were surprising. Frogs do not regenerate new legs naturally. But these frogs began to grow new limbs. About half of each cut-off leg grew back again. New bones and muscles developed. This research has led doctors to new ways of treating cut-off fingers. Doctors have observed, for example, that many children and some adults will regrow the top of a finger if the wound is left open.

单选题Do you follow what I am saying?

单选题She was grateful to him for being so good to her.

单选题The food is {{U}}insufficient{{/U}} for three people．

单选题Preventing Child Maltreatment Child maltreatment is a global problem with serious life-long consequences. There are no reliable global estimates or the prevalence of child maltreatment. Data for many countries, especially low-and middle-income countries, are lacking. Child maltreatment is complex and difficult to study. Current estimates vary widely depending on the country and the method of research used. Nonetheless, international studies reveal that approximately 20% of women and 5%-10% of men report being Sexually abused as children, while 25%-50% of all children report being physically abused. Additionally, many children are subject to emotional abuse (sometimes referred to as psychological abuse). Every year, there are an estimated 31,000 homicide deaths in children under 15. This number underestimates the true extent of the problem, as a significant proportion of deaths due to child maltreatment are incorrectly attributed to falls, burns and drowning. Child maltreatment causes suffering to children and families and can have long-term consequences. Maltreatment causes stress that is associated with disruption in early brain development. Extreme stress can impair the development of the nervous and immune systems. Consequently, as adults, maltreated children are at increased risk for behavioural, physical and mental health problems. Via the behavioural and mental health consequences, maltreatment can contribute to heart disease, cancer, suicide and sexually transmitted infections. Beyond the health consequences of child maltreatment, there is an economic impact, including costs of hospitalization, mental health treatment, child welfare, and longer-term health costs. It is important to emphasize that children are the victims and are never to blame for maltreatment. A number of characteristics of an individual child may increase the likelihood of being maltreated, such as being either under four years old or an adolescent, being unwanted, or failing to fulfil the expectations of parents and having special needs, crying persistently or having abnormal physical features.

单选题The department chairman refused to authorize the requisition.

单选题He is renowned for his skill.

单选题Warm People Likely to Keep Cold at Bay Staying positive through the cold season could be your best defense against getting ill, new study findings suggest. In an experiment that exposed healthy volunteers to a cold or flu virus, researchers found that people with a generally sunny disposition were less likely to fall ill. The findings, published in the journal Psychosomatic Medicine, build on evidence that a "positive emotional style" can help ward off the common cold and other illnesses. Researchers believe the reasons may be both objective as in happiness boosting immune function and subjective as in happy people being less troubled by a scratchy throat or runny nose. "People with a positive emotional style may have different immune responses to the virus," explained lead study author Dr Sheldon Cohen of Carnegie Mellon University in Pittsburgh. "And when they do get a cold, they may interpret their illness as being less severe. " Cohen and his colleagues had found in a previous study that happier people seemed less susceptible to catching a cold, but some questions remained as to whether the emotional trait itself had the effect. For the new study, the researchers had 193 healthy adults complete standard measures of personality traits, self-perceived health and emotional "style". Those who tended to be happy, energetic and easy-going were judged as having a positive emotional style, while those who were often unhappy, tense and hostile had a negative style. The researchers gave them nasal drops containing either a cold virus or a particular flu virus. Over the next six days, the volunteers reported on any aches, pains, sneezing or congestion they had, while the researchers collected objective data, like daily mucus production. Cohen and his colleagues found that based on objective measures of nasal woes, happy people were less likely to develop a cold.

单选题Eating Potatoes Gives Your Immune System a Boost Eating potatoes is not only good for bowel health, but also for the whole immune system, especially when they come in the form of a potato salad or eaten cold. In a study on an animal model, researchers in Spain found that pigs fed large quantities of raw potato starch (RPS) not only had a healthier bowel, but also decreased levels of white blood cells, such as leucocytes and lymphocytes in their blood. White blood cells are produced as a result of inflammation or disease, generally when the body is challenged. The general down-regulation of leucocytes observed by the Spanish researchers suggests an overall beneficial effect, a generally more healthy body. The reduction in leucocyte levels was about 15 percent. Lower lymphocyte levels are also indicative of reduced levels of inflammation, but the observed reduction in both lymphocyte density and lymphocyte apoptosis is surprising. In what was the longest study of its kind, pigs were fed RPS over 14 weeks to find out the effect of starch on bowel health. "The use of raw potato starch in this experiment is designed to simulate the effects of a diet high in resistant starch, " said study leader Jose Francisco Perez at the Universitat Autonoma de Barcelona, Spain. Humans do not eat raw potatoes, but they do eat a lot of foods that contain resistant starch, such as cold boiled potatoes, legumes, grains, green bananas, pasta and cereals. About 10 percent of the starch eaten by human is resistant starch — starch that is not digested in the small intestine and so is shunted into the large intestine where it ferments. Starch consumption is thought to reduce the risk of large bowel cancer and may also have an effect on irritable bowel syndrome (IBS). Immunology expert Lena Ohman's team previously found that the overall lymphocyte levels do not vary for IBS patients, but that lymphocytes are transferred from the peripheral blood to the gut, which support the hypothesis of IBS being at least partially an inflammatory disorder. She says the decrease in lymphocytes observed by the Spanish is therefore interesting, and a diet of resistant starch may be worth trying in IBS patients. Ohman is currently at the Department of Internal Medicine, Goteborg University, Sweden. The study is published in the journal Chemistry and Industry, the magazine of the SCI.

单选题The sea was calm and {{U}}still{{/U}}. A. quite B. quiet C. yet D. rough

单选题We all think that Mary"s husband is a very dull person.

单选题I have little information （as regards） her fitness for the post.

单选题Chemical weapons are banned internationally.

单选题The United States In 1782 【51】 the United States won its independence, the bald eagle was chosen 【52】 the national bird of the new country. American leaders wanted the eagle to be a 【53】 of their country because it''s a bird of strength and courage. They chose the bald eagle because it was found all over North America and only in North America. But a little over 200 years 【54】 ,the bald eagle had almost disappeared from the country, In 1972, there were only 3,000 bald eagles in the entire United States. The reason for the birds 【55】 population was pollution, especially pollution of rivers by pesticides. Pesticides are chemicals 【56】 to kill insects and other animals that attack and destroy crops. 【57】 , rain often washes pesticides into rivers. Pesticides pollute the rivers and poison the fish. Eagles eat 【58】 and the poison 【59】 their eggs. The eggs have very thin shells and do not hatch. Eagles 【60】 only two or three eggs a year. Because many of the eggs did not 【61】 and produce more eagles, 【62】 eagles quickly 【63】 smaller. Today, the American Government and the American people are trying to protect the bald eagle. The number of bald eagles 【64】 It now appears 【65】 the American national bird will survive and remain a symbol of strength and courage.

单选题 American Sports The United States is a sports-loving nation. Sports in America take a variety of forms: organized competitive struggles, which draw huge crowds to cheer their favorite team to victory; athletic games, played for recreation anywhere sufficient space is found; and hunting and fishing. Most sports are seasonal, so that what is happening in sports depends upon the time of year. Some sports are called spectator sports, as the number of spectators greatly exceeds the number playing in the game. Baseball is the most popular sport in the US. It is played throughout the spring and summer, and professional baseball teams play well into the fall. Although no other game is exactly like baseball, perhaps the one most nearly like it is the English game of cricket. Football is the most popular sport in the fall. The game originated as a college sport more than 75 years ago. It is still played by almost every college and university in the country, and the football stadiums of some of the largest universities seat as many as 80000 people. The game is not the same as European football or soccer. In American football there are 11 players in each team, and they are dressed in padded uniforms and helmets because the game is rough and injuries are likely to occur. Basketball is the winter sport in American schools and colleges. Like football, basketball originated in the US and is not popular in other countries. Many Americans prefer it to football because it is played indoors throughout the winter and because it is a faster game. It is a very popular game with high schools, and in more than 20 states, state-wide high school matches are held yearly. Other spectator sports include wrestling, boxing, and horse-racing. Although horse-racing fans call themselves sportsmen, the accuracy of the term is questionable, as only the jockeys who ride the horses in the races can be considered athletes. The so-called sportsmen are the spectators, who do "not assemble" primarily to see the horses race, but to bet upon the outcome of each race. Gambling is the attraction of horse racing.

单选题These computer programs can {{U}}increase{{/U}} productivity.

单选题Even in a modernized country, manual work is still needed.

单选题A {{U}}diverse{{/U}} range of industry is established in Milton Keynes including many small firms.

单选题The company endured heavy financial losses.

单选题The attack on Fort Sumter near Charleston provoked a sharp response from the North, which led to the American Civil War. A. demanded B. elicited C. extracted D. defied