单选题If you want to acquire profound knowledge, you must start from the ABC.

单选题Renewable Energy Sources Today petroleum provides around 40% of the world"s energy needs, mostly fuelling automobiles. Coal is still used, mostly in power stations, to cover one-quarter of our energy needs, but it is the least efficient, unhealthiest and most environmentally damaging fossil fuel. Natural gas reserves could plug some of the gap from oil, hut reserves of that will not last into the 22nd century either. Most experts predict we will exhaust easily accessible reserves within 50 years. We could fast reach an energy crisis. We need to rapidly develop sustainable solutions to fuel our future. Less-polluting renewable energy sources offer a more practical long-term energy solution. They may benefit the world"s poor too. "Renewable" refers to the fact that these resources are not used faster than they can be replaced. The Chinese and Romans used watermills over 2,000 years ago. But the first hydroelectric dam was built in England in 1870. Hydroelectric power is now the most common form of renewable energy, supplying around 20% of world electricity. China"s Three Gorges Dam, which has just been completed, is the largest ever. At five times the size of the US"s Hoover Dam, its 26 turbines will generate the equivalent energy of 18 coal-fired power stations. It will satisfy 3% of China"s entire electricity demand. Surprisingly, some argue that hydroelectric dams significantly contribute greenhouse gases. In 2003, the first commercial power station to harness tidal currents in the open sea opened in Norway. It is designed like windmill, but others take the form of turbines. As prices fall, wind power has become the fastest growing type of electricity generation—quadrupling worldwide between 1999 and 2005. Modern wind farms consist of turbines that generate electricity. Though it will be more expensive, there is more than enough wind to provide the world"s entire energy needs. Wind farms come in onshore and offshore forms. They can often end up at spots of natural beauty, and are often unpopular with residents. And turbines are not totally benign—they can interfere with radar and leave a significant ecological footprint, altering climate and killing sea birds. Migrating birds may have more luck avoiding them. Scotland is building Europe"s largest wind farm, which will power 200,000 homes. The UK"s goal is to generate one-fifth of power from renewable sources, mainly wind, by 2020. But this may cause problems, because wind is unreliable.

单选题Energy Cycle Do you find getting up in the morning so difficult that it"s painful? This might be called laziness, but Dr. Kleitman has a new explanation. He has proved that everyone has a daily energy cycle. During the hours when you labor through your work you may say that you"re "hot". That"s true. The time of day when you feel most energetic is when your cycle of body temperature is at its peak. For some people the peak comes during the morning. For others it comes in the afternoon or evening. No one has discovered why this is so, but it leads to such familiar monologues as: "Get up, John! You"ll be late for work again!" The possible explanation to the trouble is that John is at his temperature-and-energy peak in the evening. Much family quarrelling ends when husbands and wives realize what these energy cycles mean, and which cycle each member of the family has. You can"t change your energy cycle, but you can learn to make your life fit to it better. Habit can help, Dr. Kleitman believes. Maybe you"re sleepy in the evening but you must stay up late anyway. Counteract your cycle to some extent by habitually staying up later than you want to. If your energy is low in the morning but you have an important job to do early in the day, rise before your usual hour. This won"t change your cycle, but you"ll get up steam and work better at your low point. Get off to a slow start which saves your energy. Get up with a leisurely yawn and stretch. Sit on the edge of the bed a minute before putting your feet on the floor. Avoid the trouble of searching for clean clothes by laying them out the night before. Whenever possible, do routine work in the afternoon and save tasks requiring more energy or concentration for your sharper hours.

单选题Computers The initial impact of computers was in the area of entertainment. If you walked by a video arcade in the early 1980s, you could not have failed to notice that the use of video games was growing at what some considered an alarming rate. In 1981 the movie industry grossed $3 billion, video games took in an estimated $6 billion. That gives you some idea of just how big the computer industry had become. Video games employ the same technology as personal computers, and indeed many who bought personal computers did so primarily for playing games at home, thus saving their quarters. Though video games are not as popular as they were a few years ago, they did provide consumer with their first real reason to buy PCs. A more recent computer innovation, desktop publishing, supplies one good reason for those who write for a living to buy a PC. Desktop publishing is a deceptively simple description for an extremely complex group of hardware and software tools. You can now write text, edit text, draw illustrations, incorporate photographs, design page layouts, and print a finished document with a relatively inexpensive computer and laser printer. Although the new technology offers new freedom, there is a price to be paid for this freedom. With total control comes total responsibility. In fact, the issue of social responsibility in our new computer age has long been a topic of debate among computer enthusiasts. Some people are concerned with the long-term social effects of the so-called computer revolution. Ironically, many PC pioneers who built and marketed the first machines were 60s-style advocates of social change. They claim that while personal computer technology has the potential to make society more equal, it"s having the opposite effect since upper-middle-class people can afford them and lower-class people cannot. In addition, the ways that computers are used to monitor the activities of their users have evoked anxiety about the machine. Over 7 million Americans now have their work paced, controlled, and monitored by computers. A computer is more restrictive and powerful in the way it controls people than the old-fashioned assembly line. This can lead to what some have called "tech-stress". Irritated eyes, back problems, and other physical symptoms have also been associated with the extensive use of computers. Although the personal computer may not have had the impact some predicted a decade age, the combination of computer technology with satellites and cable does promise innovations in the mass media that would have seemed astonishing just a few short years ago.

单选题The quality and number of a city's public roads offer an excellent means of Ugauging/U its prosperity.

单选题Up to now, the work has been easy. A. So B. So long C. So that D. So far

单选题Things in the henhouse changed practically overnight when McDonald's announced in 1999 that it would no longer buy eggs from producers who didn't meet its guidelines for care of chickens. Those guidelines included limiting the (51) of birds that could be kept in one (52) and prohibiting beak removal, (53) trimming just the tips. Once McDonald's had (54) the way in issuing animal care guidelines for the company's suppliers, many other giants of the fast food industry rapidly followed suit, including Burger King, Taco Bell, Pizza Hut, Wendy's, A＆W, and KFC. Now, the American Meat Institute has (55) welfare guidelines and audit (56) for cattle, pigs, and chickens. And the European Union, representing our foreign customers, is also weighing in with, among other things, legislation banning (57) use of crates to house pregnant sows, effective in 2013. Questions about animal care (58) with the explosive growth in large scale livestock farms, (59) spurred customers to complain about animals being treated as "factory parts." That spurred ARS and the livestock industry to take a proactive approach to addressing animal welfare issues, making sure that guidelines are based on facts (60) through scientific research. The goal is to share research findings with the retail food industry and others so that the livestock industry can improve its (61) guidelines. Ten years ago, to address these concerns, ARS started a research program on livestock behavior and stress. The scientists involved were tasked with finding out whether modem farming practices were (62) stressing animals. And if so, could scientific methods be developed lo measure this stress so that (63) could be evaluated objectively rather than subjectively? A decade later, the (64) answer is "yes" to both questions. Many had expected the answer to be "no" on both counts, but science works independently (65) people's opinions.

单选题Kit Carson, an American frontiersman, was one of the most sensational heroes of the Old West. A. exciting B. distracting C. enigmatic D. ostentatious

单选题The leaves have been swept into huge heaps .

单选题The reason for their unusual behavior remains a puzzle .

单选题What kinds of {{U}}products{{/U}} were sold in this shop?

单选题By providing legal representation, the American Civil Liberties Union works to defend citizens against breaches of their civil rights.

单选题Paragraph 5_____

单选题The audience at the music hall Uapplauded/U enthusiastically after the piano solo.

单选题Some people would like to do shopping on Sundays since they expect to pick up wonderful articles in the market.A. batteriesB. bargainsC. basketsD. barrels

单选题The President made a brief visit to Beijing.

单选题People from many places were drawn to the city by its growing economy.

单选题Many scientists have been probing psychological problems. A. solving B. exploring C. settling D. handling

单选题The only access ______ that mountainous village is through a muddy path.A. forB. toC. acrossD. in

单选题Computer Mouse The basic computer mouse is 1 amazingly clever invention with a relatively simple design that allows us to point at things on the computer and it is very productive. Think of all the things you can do with a mouse like selecting text for copying and pasting, drawing, and even scrolling(滚动) on the page with the newer mice with the wheel. Most of us use the computer mouse daily without stopping to think how it 2 until it gets dirty and we have to learn how to 3 it. We learn to point at things 4 we learn to speak, so the mouse is a very natural pointing device. Other computer pointing devices include light pens, graphics tablets and touch screens, but the mouse is still our workhorse. The computer mouse was 5 in 1964 by Douglas Englehart of Stanford University. As computer screens became more popular and arrow keys were used to move around a body of text, it became clear that a pointing device that allowed easier motion through the text and even selection of text would be very useful. The introduction of the mouse, with the Apple Lisa computer in 1983, really started the computer public on the road to relying on the mouse 6 routine computer tasks. How does the mouse work? We have to start at the bottom, so think upside down for now. It all starts with the mouse ball. As the mouse ball in the bottom of the mouse rolls over the mouse pad, it presses against and turns two shafts (轴). The shafts are connected to wheels with several small holes in them. The wheels have a pair of small electronic light-emitting devices 7 light-emitting diodes (LED) mounted on either side. One LED sends a light beam to the LED on 8 side. As the wheels spin and a hole rotates by, the light beam gets through to the LED on the other side. But a moment 9 the light beam is blocked until the next hole is in place. The LED 10 a changing pattern of light, converts the pattern 11 an electronic signal, and sends the signal to the computer through wires in a cable that goes out of the mouse body. This cable is the tail that helps give the mouse its name. The computer interprets the signal to tell it where to position the cursor on the computer 12 . So far we have only discussed the basic computer mouse that 13 of you probably have or have used. One problem with this design is that the mouse gets dirty as the ball rolls over the surface and picks up dirt. 14 you have to clean your mouse. The newer optical mice 15 this problem by having no moving parts.