单选题The police tried in vain to break up the protest crowds in front of the government building.

单选题Our examination has been postponed until next Friday.A. put onB. put downC. put offD. put in

单选题If headaches only Uoccur/U at night, lack of fresh air is often the cause.

单选题Customers often {{U}}defer{{/U}} payment for as long as possible.

单选题Marvelous Metamaterials Invisibility cloaks would have remained impossible, forever locked in science fiction, had it not been for the development of metamaterials. In Greek, "meta" means beyond, and metamaterials can do things beyond what we see in the natural world-like shuffle light waves around an object, and then bring' them back together. If scientists ever manage to build a full-fledged invisibility cloak, it will probably be made of metamaterials. "We are creating materials that don't exist in nature, and that have a physical phenomenon that doesn't exist in nature," says engineer Dentcho Genov. "That is the most exciting thing." Genov designs and builds metamaterials such as those used in cloaking at Louisiana Tech University in Ruston, Louisiana. An invisibility cloak will probably not be the first major accomplishment to come from the field of metamaterials. Other applications are just as exciting. In many labs, for example, scientists are working on building a hyperlens. A lens is a device, usually made of glass that can change the direction of light waves. Lenses are used in microscopes and cameras to focus light, thus allowing a researcher to see small things or a photographer to capture image of things that are far away. A hyperlens, however, would be made of metamaterials. And since metamaterials can do things with light that ordinary materials can't, the hyperlens would be a powerful too 1. A hyperlens would allow researchers to see things at the smallest scale imaginable, as small as the wavelength of visible light. Genov points out that the science of metamaterials is driven by the imagination. If someone can think of an idea for a new behavior for fight, then the engineers can find a way to design a device using metamaterials. "We need people who can imagine," he says. Since 2006, many laboratories have been exploring other kinds of metamaterials that don't involve just visible light. In fact, scientists are finding that almost any kind of wave may respond to metamaterials. At the Polytechnic University of Valencia in Spain, Jose Sanchez-Dehesa is working with acoustics, or the science of sound. Just as an invisibility cloak shuffles waves of light, an "acoustic" cloak would shuffle waves of sound in a way that's not found in nature. In an orchestra hall, for example, an acoustic cloak could redirect the sound waves so someone sitting behind a column would hear the same concert as the rest of the audience without distortion. Sanchez-Dehesa, an engineer, recently showed that it's possible to build such an acoustic cloak, though he doubts we'll see one any time soon. "In principle, it is possible," he says, "but it might be impossible to make one." he adds. Other scientists are looking into ways to use larger metamaterials as shields around islands or oil rigs as protection from tsunamis. A tsunami is a giant destructive wave. The metamaterial would redirect the tsunami around the rig or island, and the wave would resume its energy on the other side without causing any harm.

单选题Ms. Breen has been living in town for only one year, yet she seems to be familiar with everyone who comes to the store.

单选题Fitness Movement The fitness movement that began in the late 1960s and early 1970s centered around aerobic exercise. Millions of individuals became engaged in a variety of aerobic activities, and 1 thousands of health spas developed around the country to capitalize on his 2 interest in fitness, particularly aerobic dancing for females. A number of fitness spas existed 3 to this aerobic fitness movement, even a national chain with spas in most major cities. However, their 4 was not on aerobics, but rather on weight-training programs designed to develop muscular mass, 5 , and endurance in their primarily male 6 . These fitness spas did not seem to benefit 7 from the aerobic fitness movement to better health, since medical opinion suggested that weight-training programs 8 few, if any, health benefits. In recent years, however, weight training has again become increasingly 9 for males and for females. Many 10 programs focus not only on developing muscular strength and endurance but on aerobic fitness as well. 11 , most physical fitness tests have usually included measures of muscular strength and endurance, not for health related reasons, but primarily 12 such fitness components have been related to performance in athletics. 13 , in recent years, evidence has shown that training programs designed primarily to improve muscular strength and endurance might also offer some health 14 as well. The American College of Sports Medicine now 15 that weight training be part of a total fitness program for healthy Americans.

单选题The man was sent to prison for driving {{U}}recklessly{{/U}}.

单选题Jack was dismissed. A. fired. B. fined C. exhausted D. criticized

单选题From my standpoint , you know, this thing is just ridiculous.

单选题Please be careful when you are drinking coffee in case you smudge the new carpet.A. crashB. polluteC. contaminateD. stain

单选题Nobody likes taking exams; exams (51) our own language can be stressful enough but somehow exams in a foreign language always seem to (52) more worry and anxiety. Well, the good news is that, if you (53) some simple steps, taking English language exams can be really quite (54) It won't exactly be fun, but it certainly shouldn't give you too many headaches or (55) nights. If you are planning to (56) one of the well - known exams such as Cambridge First Certificate, you will probably find that there's a preparation course (57) at a school near you. Cheek that the school has a good (58) of exam success and that the teacher is (59) . It is a good idea to ask if you will be given homework and (60) your written work will be marked by a teacher (61) knows the level of English (62) by the exam. If you take (63) exam preparation course, your teacher will give you all the information you need and you will find that (64) in a class helps you to study more effectively. But you will still need to (65) a lot of work yourself after all, the teacher can't take the exam for you !

单选题 The Spanish Flu Epidemic If you're worried about the possibility of a coming bird flu epidemic, you can take comfort in the fact that humanity has survived a similar influenza epidemic in the past. Starting its rounds at the end of World War I, the 1918 flu killed an estimated 50 million people. Popularly known as the Spanish Flu, this type of influenza was far worse than your common cold. Normally, influenza only kills those who are more vulnerable to disease, such as newborns, the old or the sick. However, the Spanish Flu was prone to killing the young and healthy. Often it would disable its victims in hours; within a day, they would be dead, typically from extreme cases of pneumonia (肺炎). The Spanish Flu was quite nasty-fast-spreading and deadly. It managed to spread across the globe, devastating the world. Then suddenly, after two years ravaging (蹂躏) the Earth, it disappeared as quickly as it had arisen. Despite its nickname, the Spanish Flu did not originate in Spain. Its true origins are unknown. Some believe it started in US forts and then spread to Europe as America joined the war; others think that it populated the trenches of the English and the French and eventually broke out in 1918. Regardless of where it started, eventually a fifth of the world population suffered the disease, with a global mortality rate (死亡率) estimated at 2.5% of the population. Modernity was partly to blame for the quick spread of the disease. It passed throughout the world on trade routes and shipping lines. It hit Northern America, Europe, Asia, Africa and the South Pacific. The war did not help at all-the movement of supplies and troops aided the spread of the Spanish Flu, as well as the trench warfare. Imagine the speed at which a virus can spread in a crowded ditch. The fast emergence of the virus in the trenches caused some soldiers to believe that the Spanish Flu was a new form of biological warfare. Luckily, the Spanish Flu simply vanished by 1920. It is believed the flu simply ran out of fuel to spread.

单选题Eleanor Roosevelt urged legislation to assist the poor and oppressed.

单选题The drama {{U}}depicts{{/U}} those conditions at the turn of the century.

单选题The megaphone makes the voice sound louder because it points sound waves in one direction and keeps them from spreading out in all directions.

单选题The substance can be added to gasoline to accelerate the speed of automobiles,

单选题 {{B}}Shopping online{{/B}} Internet retailer AMAZON. COM on Wednesday released a rare and revealing peek at its customers' shopping habits, taken from a September e-mail poll of 2,072 customers of its French, German and United kingdom sites. The company said the research was done in the name of improving customer service. "We have to learn from the nuances and idiosyncrasies of each nation's shopping habits to see how we can serve our customers better this Christmas, "said Robin Terrell, managing director of Amazon. co. uk. The findings paint a unique picture of the shopping habits of the world's largest online retailer, plus their motivation and preferences. For instance, the round-the-clock convenience of e-commerce ranked above price as the prime motivating factor for online shoppers, the company said. And more purchases are made from home than work. According to the poll results, 31 percent of shoppers plunk down their credit card during work hours, against 67 percent at home or in a home office. The notable exception is Ireland, where 46 percent of shoppers polled do so while at their office desk. The British are the second worst offenders, with 40 percent admitting to on-the-job shopping, while the Danes are the most honorable, with one in five making a purchase while on the job. At 53 percent, the majority of Europeans shop in the evenings at home. Austrians and Germans are the most avid night owl shoppers, with 63 percent and 62 percent, respectively, reporting this habit. The Germans, though, are the least likely group to shop online after 10 p. m., the study said. Other findings include: the French and British are most active shoppers with three in 10 visiting e-commerce sites more than 10 times per month; and the Irish have the greatest concentration of shopaholics—one in ten hit the cyber—shops more than 20 times a month, twice the European average. In contrast, just 1 percent of Italians polled shop online more than 20 times per month. The least active group are the Dutch, with 25 percent reporting they shop online once a month or less. But among the senior set, Dutch "silver surfers"—Internet users above the age of 50—shop online 20 percent of the time, Amazon said. The French, meanwhile, like to get an early and late crack at online shopping with 18 percent logging on after 10 p.m. and 11 before 10 a. m., the company said. And what about the Swedes? According to the survey, the Swedes are most likely among those polled to buy something they hadn't planned on purchasing.

单选题They are endeavoring to reform the present rules.A. tryingB. workingC. doingD. making

单选题Customers may also be permitted to overdraft their current accounts for a short period in anticipation of a credit item coming in.