单选题What really works to make sustainable changes in diet and lifestyle? It's probably not what you think. Years of clinical research proves that the real keys are pleasure, joy and freedom, not our power of will or austerity (苦行). Joy of living is sustainable; fear of dying is not. Why? Because life is to be enjoyed. There's no point in giving up something you enjoy unless you get something back that's even better, and quickly. When people eat more healthfully, exercise, quit smoking, manage stress better, and love more, they find that they feel so much better, so quickly, it reconstruct the reason for making these changes from fear of dying to joy of living. Fortunately, the latest studies show how dynamic and powerful are the mechanisms that control our health and well-being. When you exercise and eat right: Your brain receives more blood flow and oxygen, so you become smarter, think more clearly, have more energy, and need less sleep. Two studies showed that just walking for three hours per week for only three months caused so many new nerve cells to grow that it actually increased the size of people's brains! Your face receives more blood flow, so your skin glows more and wrinkles less. You look younger and more attractive. In contrast, an unhealthy diet, lasting emotional stress and smoking reduce blood flow to your face so you age more quickly. Smoking accelerate aging because nicotine (尼古丁) causes your blood vessel to become narrower, which decreases blood flow to your face and makes it wrinkle prematurely. This is why smokers look years older than they really are. One of the most interesting findings in this study was that the mothers' perceptions of stress were more important than what was objectively occurring in their lives. The researchers made a survey among women and asked them to rate on a three-point scale how stressed they felt each day, and how out of control their lives felt to them. The women who perceived that they were under heavy stress had significantly shortened and damaged telomeres (染色体端粒) compared with those who felt more relaxed. Conversely, some of the women who felt relaxed despite raising a disabled child had more normal-appearing telomeres. In other words, if you feel stressed, you are stressed.

单选题Which of the following may NOT be the reason of eating disorders?

单选题The author presents the passage by

单选题{{B}}Text 2{{/B}} IT is a startling claim, but one that Congresswoman Deborah Pryce uses to good effect: the equivalent of two classrooms full of children are diagnosed with cancer every day. Mrs Pryce lost her own 9-year-old daughter to cancer in 1999. Pediatric cancer remains a little-understood issue in America, where the health-care debate is consumed with the ills, pills and medical bills of the elderly. Cancer kills more children than any other disease in America. Although there have been tremendous gains in cancer survival rates in recent decades, the proportion of children and teens diagnosed with different forms of the disease increased by almost a third between 1975 and 2001. Grisly though these statistics are, they are still tiny when set beside the number of adult lives lost to breast cancer (41,000 each year) and lung cancer (164,000). Advocates for more money for child cancer prefer to look at life-years lost. The average age for cancer diagnosis in a young child is six, while the average adult is diagnosed in their late 60s. Robert Arceci. a pediatric cancer expert at Johns Hopkins, points out that in terms of total life-years saved, the benefit from curing pediatric cancer victims is roughly the same as curing adults with breast cancer. There is an obvious element of special pleading in such calculations. All the same, breast cancer has attracted a flurry of publicity, private fund-raising and money from government. Childhood cancer has received less attention and cash. Pediatric cancer, a term which covers people up to 20 years old, receives one-twentieth of the federal research money doled out by the National Cancer Institute. Funding, moan pediatric researchers, has not kept pace with rising costs m the field, and NCI money for collaborative research will actually be cut by 3% this year. There is no national pediatric cancer registry that would let researchers track child and teenage patients through their lives as they can do in the case of adult sufferers. A pilot childhood-cancer registry is in the works. Groups like Mr Reaman's now get cash directly from Congress. But it is plainly a problem most politicians don't know much about. The biggest problem could lie with 15-19-year-olds. Those diagnosed with cancer have not seen the same improvement in their chances as younger children and older adults have done. There are some physical explanations for this: teenagers who have passed adolescence are more vulnerable to different sorts of cancer. But Archie Bleyer, a pediatric oncologist at the M.D. Anderson Cancer Centre in Texas, has produced some data implying that lack of health insurance plays a role. Older teenagers and young adults are less likely to be covered and checked regularly.

单选题Good teachers matter. This may seem obvious to anyone who has a child in school or, for that matter, to anyone who has been a child in school. For a long time, though, researchers couldn’t actually prove that teaching talent was important. But new research finally shows that teacher quality is a close cousin to student achievement: A great teacher can cram one-and-a-half grades’ worth of learning into a single year, while laggards are lucky to accomplish half that much. Yet, while we know now that better teachers are critical, flaws in the way that administrators select and retain them mean that schools don’t always hire the best. Failing to recognize the qualities that make teachers truly effective and to construct incentives to attract and retain more of these top performers has serious consequences. Higher salaries draw more weak as well as strong applicants into teaching — applicants the current hiring system can’t adequately screen. Unless administrators have incentives to hire the best teachers available, it’s pointless to give them a larger group to choose from. Study after study has shown that teachers with master’s degrees are no better than those without. Job experience does matter, but only for the first few years, according to research by Hoover Institution’s Eric A. Hanushek. A teacher with 15 years of experience is no more effective, on average, than a teacher with five years of experience, but which one do you think is paid more? This toxic combination of rigid pay and steep rewards for seniority causes average quality to decline rather than increase as teacher groups get older. Top performers often leave the field early for industries that reward their excellence. Mediocre teachers, on the other hand, are soon overcompensated by seniority pay. And because they are paid more than their skills command elsewhere, these less-capable pedagogues settle in to provide many years-of ineffectual instruction. So how can we separate the wheat from the chaff in the teaching profession? To make American schools competitive, we must rethink seniority pay, the value of master’s degrees, and the notion that a teacher can teach everything equally well — especially math and science — without appropriate preparation in the subject. Our current education system is unlikely to accomplish this dramatic rethinking. Imagine, for a moment, that American cars had been free in recent decades, while Toyotas and Hondas sold at full price. We’d probably be driving Falcons and Corvairs today. Free public education suffers from a lack of competition in just this way. So while industries from aerospace to drugs have transformed themselves in order to compete, public schooling has stagnated. School choice could spark the kind of reformation this industry needs by motivating administrators to hire the best and adopt new strategies to keep top teachers in the classroom. The lesson that good teachers matter should be taught, not as a theory, but as a practice.

单选题According to Hofstadter, American teachers

单选题According to the text, sustainable economy

单选题One reason human beings can thrive in all kinds of climates is that they can control the qualities of the air in the enclosed spaces in which they live. Air conditioning is the use of mechanical systems to (1) that control in such places (2) homes, offices, theaters, institutions, factories, airplanes, and automobiles. The most familiar type of air conditioning is summertime cooling. Although important, this is (3) one of several aspects of air conditioning. Other applications (4) . the control of the humidity (or air moisture), cleanliness, circulation of the air, and heating. Tests have (5) that people generally feel best (6) certain temperature, humidity, and air velocity conditions. Temperatures can (7) from 21.5° C with 70 percent relative humidity to 28° C with 30 percent relative humidity. Relative humidity is the (8) of moisture in the air (9) a specific temperature compared (10) the amount it could hold at that temperature. (11) air velocities range from 4.5 to 10.5 meters per minute. It is also desirable that an air conditioner (12) dust, pollen, smoke, and odors from the air. In many industrial environments, air conditioning is essential. Most print shops, for example, (13) constant humidity in order to control paper shrinkage and (14) the (15) operation in some processes. Libraries, especially ones with rare books, require air control to (16) the physical quality of their collections. Bakeries and the tobacco and cotton industries require high humidity (17) their products, and perishables such as fruits must be stored in cool, dry rooms. Some electronic components, drugs, and chemicals must be manufactured (18) the air is as free as possible (19) dust and other particles. Air conditioning is (20) in hospitals, especially in operating rooms.

单选题Why is electrical technology mentioned in the third paragraph?

单选题In order to reduce the asbestos risk, the report gives the following suggestions except______

单选题Shortages of flu vaccine are nothing new in America, but this year's is a whopper. Until last week, it appeared that 100 million Americans would have access to flu shots this fall. Then British authorities, concerned about quality-control problems at a production plant in Liverpool, barred all further shipments by the Chiron Corp. Overnight, the U. S. vaccine supply dwindled by nearly half and federal health officials found themselves making an unusual plea. Instead of beseeching us all to get vaccinated, they're now urging most healthy people between the ages of 2 and 64 not to. "This reemphasizes the fragility of our vaccine supply," says Dr. Martin Myers of the National Network for Immunization Information, "and the lack of redundancy in our system." Why is such a basic health service so easily knocked out? Mainly because private companies have had little incentive to pursue it. To create a single dose of flu vaccine, a manufacturer has to grow live virus in a 2-week-old fertilized chicken egg, then crack the egg, harvest the virus and extract the proteins used to provoke an immune response. Profit margins are narrow, demand is fickle and, because each year's flu virus is different, any leftover vaccine goes to waste. As a result, the United States now has only two major suppliers (Chiron and Aventis Pasteur)—and when one of them runs into trouble, there isn't much the other can do about it. "A vaccine maker can't just call up and order 40 million more fertilized eggs, " says Manon Cox, of Connecticut-based Protein Sciences Corp. "There's a whole industry that's scheduled to produce a certain number of eggs at. a certain time." Sleeker technologies are now in the works, and experts are hoping that this year's fiasco will speed the pace of innovation. The main challenge is to shift production from eggs into cell cultures—a medium already used to make most other vaccines. Flu vaccines are harder than most to produce this way, but several biotech companies are now pursuing this strategy, and one culture-based product (Solvay Pharmaceuticals' Invivac) has been cleared for marketing in Europe. For Americans, the immediate challenge is to make the most of a limited supply. The government estimates that 95 million people still qualify for shots under the voluntary restrictions announced last week. That's nearly twice the number of doses that clinics will have on hand, but only 60 million Americans seek out shots in a normal year. In fact, many experts are hoping the shortage will serve as an awareness campaign—encouraging the people who really need a flu shot to get one.