单选题The wild animals are enclosed in small cages in the zoo.A. limitedB. boundedC. restrictedD. confined

单选题 Powering a City? It's a Breeze. The graceful wooden windmills that have broken up the flat Dutch landscape for centuries—a national symbol like wooden shoes and tulips—yielded long ago to ungainly metal-pole turbines. Now, windmills are breaking into a new frontier. Though still in its teething stages, the "urban turbine" is a high-tech windmill designed to generate energy from the rooftops of busy cities. Lighter, quieter, and often more efficient than rural counterparts, they take advantage of the extreme turbulence and rapid shifts in direction that characterize urban wind patterns. Prototypes have been successfully tested in several Dutch cities, and the city government in the Hague has recently agreed to begin a large-scale deployment in 2003. Current models cost US $8,000 to US $12,000 and can generate between 3,000 and 7,000 kilowatt hours of electricity per year. A typical Dutch household uses 3,500 kilowatt hours per year, while in the United States, this figure jumps to around 10,000 kilowatt hours. But so far, they are being designed more for public or commercial buildings than for private homes. The smallest of the current models weigh roughly 200 kilograms and can be installed on a roof in a few hours without using a crane. Germany, Finland and Denmark have also been experimenting with the technology, but the ever-practical Dutch are natural pioneers in urban wind power mainly because of the lack of space. The Netherlands, with 16 million people crowded into a country twice the size of Slovenia, is the most densely populated in Europe. Problems remain, however, for example, public safety concerns, and so strict standards should be applied to any potential manufacturer. Vibrations are the main problem in skyscraper-high turbine. People don't know what it would be like to work there, in an office next to one of the big turbines. It might be too hectic. Meanwhile, projects are under way to use minimills to generate power for lifeboats, streetlights, and portable generators. "I think the thing about wind power is that you can use it in a whole range of situations," said Corin Millais, of the European Wind Energy Association. "It's a very local technology, and you can use it right in your backyard, but I don't think anybody wants a nuclear power plant in their backyard."

单选题He demolished my arguments in minutes.

单选题MRI may make operating on the patient ______.

单选题He was persuaded to {{U}}give up{{/U}} the idea. A. mention B. accept C. consider D. drop

单选题The Weddell seal of Antarctica can dive to a depth of about, 1,600 feet and remain {{U}}submerged{{/U}} for as long as an hour and ten minutes.

单选题Next semester, Susan must take three compulsory courses.A. formalB. voluntaryC. practicalD. required

单选题When we visited the country, our Uprincipal/U impression was one of poverty and hardship.

单选题As he had already been accustomed to living in the countryside, Jackson refused to move to the city. A. used to B. got used to C. been fond to D. preferred

单选题There are two great mysteries about the beach. One is why human beings flock there by thousands, only to prostrate(俯卧) themselves in dense packs of glistening flesh. The other is why the sand goes there. Strange as it seems, oceanographers have never really understood why sand piles up on the shore. Now Douglas Inman and Daniel Conley think they have solved the puzzle. The puzzle had to do with waves. Though it might seem intuitive that waves carry water to shore, and sand along with it, it's not that simple. The crest(浪尖)of a passing wave lifts a given hit of water upward and landward, but the ensuing trough(波谷) pushes the water back down and Out to sea. Near the bottom, there the sand is, the water was always assumed to just slide back and forth—and the sand with it. "If you take a very aloof look at a beach," says Inman, "you'll realize that if the two motions move sand back and forth the same amount, then all the sand should end up in deep water.' So for beaches to exist, the crest's onshore flow must somehow move enough sand up the beach to counter the seaward tug of both the trough and gravity . The pressure changes in the sand bed, Inman and Conley think, are the key to beach creation. They found that sand doesn't just slide back and forth with each passing wave. Under a trough, it does slide seaward, in a thin layer just above the bottom. But under a crest its movement is often more elaborate. The higher pressure under a crest—higher because the water is piled higher—forces water into the porous(多孔的) sand. This creates strong whirlpools just above the sand, which help loosen it. As the crest passes overhead, the sand first rushes across the bottom; then it abruptly turns violent lifting off the bottom in large, boiling bunches. Finally, just after the crest passes, the sand explodes up into the great water column. The boiling and rushing move more sand than the backsliding under a trough, so there's a net movement of sand toward the shore.

单选题There is an abundant supply of cheap labor in this country.

单选题Mary looked pale and weary. A. iii B. tired C. worried D. peaceful

单选题When the car accident happened,we were all horrifiedA. take outB. take placeC. take inD. take away

单选题Botany, the study of plants, occupies a peculiar position in the history of human knowledge. We don't know what our Stone Age ancestors knew about plants, but from what we can observe of preindustrial societies that still exist, a detailed learning of plants and their properties must be extremely ancient. This is logical. Plants are the basis of the food pyramid for all living things, even for other plants. They have always been enormously important to the welfare of people, not only for food, but also for clothing, weapons, tools, dyes, medicines, shelter, and many other purposes. Tribes living today in the jungle of the Amazon recognize hundreds of plants and know many properties of each. To them botany has no name and is probably" not even recognized as a special branch of "knowledge" at all, "Botany" is the science thatA. studies existing tribes.B. studies ancient way of living.C. studies preindustrial societies.D. studies plants.

单选题Marsha confessed that she knew nothing of computer.A. reportedB. admittedC. hopedD. answered

单选题The soldier displayed remarkable courage in the battle.

单选题In temperate regions the growth rings on turtles’ epidermal plates reflect seasonal variations in growth. A. indicate B. stimulate C. include D. prevent

单选题Cell Phones Increase Traffic, Pedestrian Fatalities Cell phones are a danger on the road in more ways than one. Two new studies show that talking on the phone while traveling, whether you're driving or on foot is increasing both pedestrian deaths and those of drivers and passengers, and recommend crackdowns on cell use by both pedestrians and drivers. The new studies, lead-authored by Rutgers University, Newark, Economics Professor Peter D Loeb, relate the impact of cell phones on accident fatalities to the number of cell phones in use, showing that the current increase in deaths resulting from cell phone use follows a period when cell phones actually helped to reduce pedestrian and traffic fatalities. However, this reduction in fatalities disappeared once the numbers of phones in use reached a "critical mass" of 100 million, the study found. These studies looked at cell phone use and motor vehicle accidents from 1975 through 2002, and factored in a number of variables, including vehicle speed, alcohol consumption, seat belt use, and miles driven. The studies found the cell phone-fatality correlation to be true even when including factors such as speed, alcohol consumption, and seat belt use. Loeb and his co-author determined that, at the current time, cell phone use has a "significant adverse effect on pedestrian safety" and that "cell phones and their usage above a critical thresholds adds to motor vehicle fatalities." In the late 1980s and part of the 1990s, before the numbers of phones exploded, cell phone use actually had a "life-saving effect" in pedestrian and traffic accidents, Loeb notes. "Cell-phone users' were able to quickly call for medical assistance when involved in an accident. This quick medical response actually reduced the number of traffic deaths for a time," Loeb hypothesizes. However, this was not the case when cells were first used in the mid-1980s, when they caused a "life-taking effect" among pedestrians, drivers and passengers in vehicles. In those early days, when there were fewer than a million phones, fatalities increased, says Loeb, because drivers and pedestrians probably were still adjusting to the novelty of using them, and there weren't enough cell phones in use to make a difference in summoning help following an accident, he explains. The "life-saving effect" occurred as the volume of phones grew into the early 1990s, and increasing numbers of cells were used to call 911 following accidents, leading to a drop in fatalities, explains Loeb. But this life-saving effect was canceled out once the numbers of phones reached a "critical mass" of about 100 million and the "life-taking effect" increased accidents and fatalities outweighed the benefits of quick access to 911 services, according to Loeb. Loeb and his co-authors used econometric models to analyze data from a number of government and private studies. He and his co-authors recommend that governments consider more aggressive policies to reduce cell phone use by both drivers and pedestrians, to reduce the number of fatalities.

单选题The robotic technology for surgeries on people has brought a handsome profit to Medrobotics.