单选题You should cultivate the habit of reading carefully.

单选题The ground on which the church stands has always been regarded as Usacred/U.

单选题From my {{U}}standpoint{{/U}}, you know, this thing is just funny. A.position B.point of view C.knowledge D.opinion

单选题Weaving with Light In the Sierra Madre mountain range of west central Mexico, the native Huichol people live much the way their ancestors did—without electricity. That"s because it"s too expensive to string power lines to the remote mountain areas where they live. To help support themselves, the Huichol create beautiful artwork. They sell their art in cities hundreds of miles away from their villages. And without electricity—at home or on the road, they can only Work during daylight hours. When it gets dark, they must stop whatever they"re doing. Now, a team of scientists, designers, and architects is using new technologies to provide the Huichol with light after the sun sets. The scientists" technique involves weaving tiny electronic crystals into fabrics that can be made into clothes, bags, or other items. By collecting the sun"s energy during the day, these lightweight fabrics provide bright white light at night. Their inventors have named the fabrics "Portable Lights." Portable Lights have the potential to transform the lives of people without electricity around the world, says project leader Sheila Kennedy. "Our invention," Kennedy says, "came from seeing how we could transform technology we saw every day in the United States and move it into new markets for people who didn"t have a lot of money." At the core of Portable Light technology are devices called high-brightness light-emitting diodes, or HB LEDs. These tiny lights appear in digital clocks, televisions, and streetlights. LEDs are completely different from the light bulbs. Most of those glass bulbs belong to a type called incandescent lights. Inside, electricity heats a metal coil to about 2,200 degrees Celsius. At that temperature, bulbs give off light we can see. Ninety percent of energy produced by incandescent lights, however, is heat—and invisible. With all that wasted energy, bulbs burn out quickly. They are also easily broken. LEDs, on the other hand, are like tiny pieces of rock made up of molecules that are arranged in a crystal structure. When an electric current passes through an LED, the crystal structure produces light. Unlike incandescent bulbs, they can produce light of various colors. Within an LED, the type of molecules and their particular arrangement determines what color is produced.

单选题George Washington Carver was esteemed for his contributions in the fields of botany and chemistry.

单选题New secretaries came and went with Umonotonous/U regularity.

单选题There are only five minutes left, but the outcome of the match is still in doubt.

单选题Citizen Scientists Understanding how nature responds to climate change will require monitoring key life cycle event-flowering, the appearance of leaves, the first frog calls of the spring all around the world. But ecologists can't be everywhere so they're turning to non-scientists, sometimes called citizen scientists, for help. Climate scientists are not present everywhere. Because there are so many places in the world and not enough scientists to observe all of them, they're asking for your help in observing signs of climate change across the world. The citizen scientist movement encourages ordinary people too observe a very specific research interest--birds, trees, flowers budding, etc. and send their observations to a giant database to be observed by professional scientists. This helps a small number of scientists track a large amount of data that they would never be able to gather on their own. Much like citizen journalists helping large publications cover a hyper-local beat, citizen scientists are ready for the conditions where they live. All that's needed to become one is a few minutes each day or each week to gather data and send it in. A group of scientists and educators launched an organization last year called the National Phenology Network. "Phenology" is what scientists call the study of the timing of events in nature. One of the group's first efforts relies on scientists and non-scientists alike to collect data about plant flowering and leafing every year. The program, called Project BudBurst, collects life cycle data on a variety of common plants from across the United States. People participating in the project which is open to everyone record their observations on the Project BudBurst website. "People don't have to be plant experts, they just have to look around and see what's in their neighborhood," says Jennifer Schwartz, an education consultant with the project. "As we collect this data, we'll be able to make an estimate of how plants and communities of plants and animals will respond as the climate changes./

单选题Jean has made up her mind not to go to the meeting.

单选题Floods have undermined the foundation of the ancient bridge.A. destroyedB. reachedC. broadenD. covered

单选题Academic records cannot be duplicated. A. borrowed B. purchased C. copied D. rewritten

单选题His marked personality changes were {{U}}brought about{{/U}} by a series of unfortunate events.

单选题One of the reasons why business or government has not taken tough measures to stop hacking is that

单选题Remember back in 2001 when BP went" Beyond Petroleum"? It was a brilliant marketing campaign, but it had less to do with changing the company's business model than positioning Lord John Browne as the Teflon oil executive. All but a tiny fraction of BP's revenue came, and still comes from oil. So how should we take the spate of new green announcements from the world's major oil firms? In July, ExxonMobil announced big plans to grow green algae to fuel cars; last week, Chevron unveiled the world's largest carbon-sequestration project in Australia; and in recent months, Valero, Marathon, and Sunoco carried out a series of acquisitions that resulted in Big Oil controlling 7 percent of the U. S. ethanol business. Who was John Browne?A. The Teflon oil executive.B. The executive of Chevron.C. The executive of ExxonMobil.D. The executive of Big Oil.

单选题Cement was {{U}}seldom{{/U}} used in buildings of the Middle Ages. A.slight B.rarely C.originally D.occasionally

单选题 The Smog (烟雾) For over a month, Indonesia was in crisis. Forest fires raged out of control as the country suffered its worst drought for 50 years. Smoke from the fires mixed with sunlight and hot dry air to form a cloud of smog. This pollution quickly spread and within days it was hanging over neighbouring countries including Malaysia, Singapore and Thailand. When the smoke combined with pollution from factories and cars, it soon became poisonous (有毒的). Dangerous amounts of CO became trapped under the smog and pollution levels rose. People wheezed (喘息) and coughed as they left the house and their eyes watered immediately. The smog made it impossible to see across streets and whole cities disappeared as grey soot (烟灰) covered everything. In some areas, water was hosed (用胶管浇) from high-rise city buildings to try and break up the smog. Finally, heavy rains, which came came in November. Put out the fires and clear the air. But the environmental costs and health problems will remain Many people from South-Eastern Asian cities already suffer from breathing huge amounts of car exhaust fumes (汽车排放的废气) and factory pollution. Breathing problems could well increase and many non-sufferers may have difficulties for the first time. Wildlife has suffered too. In lowland forests, elephants, deer, and tigers have been driven out of their homes by smog. But smog is not just an Asian problem. In fact, the word was first used in London in 1905 to describe the mixture of smoke and thick fog. Fog often hung over the capital. Sometimes the smog was so thick and poisonous that people were killed by breathing problems or in accidents. About 4,000 Londoners died within five days as a result of thick smog in 1952.

单选题Winter is the toughest season for grasses and flowers to survive in desert.

单选题 下面的短文有15处空白，请根据短文内容为每处空白确定1个最佳选项。 An Intelligent Car Driving needs sharp eyes, keen ears, quick brain, and coordination(协调) between hands and the brain. Many human drivers have all {{U}}(51) {{/U}} and can control a fast-moving ear. But how does an intelligent car control itself? There is a virtual(虚拟) driver in the smart car. This virtual driver has "eyes", "brains", "hands" and "feet" too. The minicameras {{U}}(52) {{/U}} each side of the ear are his "eyes" which {{U}}(53) {{/U}} the road conditions ahead of it. They watch the {{U}}(54) {{/U}} to the car's left and right. There is also a highly automatic driving {{U}}(55) {{/U}} in the car. It is the built-in computer, which is the virtual driver's "brain". His "brain" {{U}}(56) {{/U}} the speeds of other moving cars near it and analyzes their positions. Basing on this information, it chooses the {{U}}(57) {{/U}} path for the intelligent ear, and gives instructions to the "hands" and "feet" to act accordingly. In this way, the virtual driver {{U}}(58) {{/U}} his car. What is the virtual driver's best advantage? He reacts {{U}}(59) {{/U}} . The minicameras are bringing {{U}}(60) {{/U}} continuously to the "brain". It completes the processing of the images with-in 100 milliseconds. {{U}}(61) {{/U}} , the world's best driver needs at least one second to react. Besides, when he takes {{U}}(62) {{/U}}, he needs one more second. The virtual driver is really wonderful. He can reduce the accident {{U}}(63) {{/U}} considerably on expressways(高速公路). In this {{U}}(64) {{/U}}, can we let him have the wheel at any time and in any place? Experts {{U}}(65) {{/U}} that we cannot do that just yet. His ability to recognize things is still limited. He can now only drive an intelligent car on expressways.

单选题Some physicists have proposed that sunspots and solar wind have negligible effects on the earth"s weather.

单选题My parents told me that we had relations in Canada and South Afric