单选题Most babies can Utake in/U a wide range of food easily.

单选题The Spanish, French, Dutch, and English all {{U}}vied for{{/U}} North American territory.

单选题Nitrogen is the most plentiful gas in the atmosphere .

单选题Certain colors when incorporated into the decor of a room can produce a cozy atmosphere. A. light B. roomy C. cluttered D. comfortable

单选题Jane said that she couldn"t tolerate the long hours.

单选题Sharks Perform a Service for Earth's Waters It is hard to get people to think of sharks as anything but a deadly enemy. They are thought to (51) people frequently. But these fish perform a (52) service for earth's waters and for human beings. Yet business and sport fishing are threatening their (53) . Some sharks are at risk of disappearing from (54) . Warm weather may influence both fish and shark activity. Many fish swim near coastal areas (55) their warm waters. Experts say sharks may follow the fish into the same areas, (56) people also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a person (57) a sea animal, such as a seal or sea lion. That is why people should not swim in the ocean when the sun goes down or comes up. Those are the (58) when sharks are looking for food. Experts also say that bright colors and shiny jewelry may cause sharks to attack. A shark has an extremely good sense of smell. It can find small amounts of substances in water, such as blood, body liquids and (59) produced by animals. These powerful (60) help sharks fred their food. Sharks eat fish, any (61) sharks, and plants that live in the ocean. Medical researchers want to learn more about the shark's body defense, and immune (62) against disease. Researchers know that sharks (63) quickly from injuries. They study the shark in hopes of finding a way to fight human disease. Sharks are important for the world's (64) . They eat injured and diseased fish. Their hunting activities mean that the numbers of other fish in ocean waters do not become too (65) . This protects the plants and other forms of life that exist in the oceans.

单选题 Save Energy at Home On the average, Americans waste as much energy as two-thirds of the world's population consumes. That's {{U}} {{U}} 1 {{/U}} {{/U}}the result of driving inefficient cars, using inefficient appliances, living and working in poorly insulated buildings. Then what can you do to improve the {{U}} {{U}} 2 {{/U}} {{/U}}? Buy energy-efficient products—Buy new appliances or electronics of the highest energy-efficiency rating. New energy efficient models may cost more initially, but have a lower operating {{U}} {{U}} 3 {{/U}} {{/U}}over their lifetimes. The most energy-efficient models {{U}} {{U}} 4 {{/U}} {{/U}}the Energy Star label which identifies products that use 20—40 percent less energy than standard new products. According to the EPA, the typical American household can save about $400 per year in {{U}} {{U}} 5 {{/U}} {{/U}}bills with products that carry the Energy Star. Switch to compact fluorescent bulbs (荧光灯)—Change the three bulbs you use {{U}} {{U}} 6 {{/U}} {{/U}}in your house to compact fluorescents. Each compact fluorescent bulb will keep half a ton of carbon dioxide out of the air over its lifetime. {{U}} {{U}} 7 {{/U}} {{/U}}, compact fluorescent bulbs last ten times as long and can save $30 per year in electricity costs. Set heating and cooling temperatures correctly—Check thermostats in your home to make sure they are {{U}} {{U}} 8 {{/U}} {{/U}}at a level that doesn't waste energy. Get an electronic thermostat that will allow your furnace to heat the house to a lower temperature when you're sleeping and return it to a more {{U}} {{U}} 9 {{/U}} {{/U}}temperature before you wake up. Turn off the lights—{{U}} {{U}} 10 {{/U}} {{/U}}lights and other electrical appliances such as televisions and radios when you're not using them. Install automatic timers for lights in case that people in your house frequently forget to turn them off when {{U}} {{U}} 11 {{/U}} {{/U}}a room. Choose renewable energy—Many consumers can now choose their energy supplier. If you have a choice, choose an electric utility that uses renewable power {{U}} {{U}} 12 {{/U}} {{/U}}, such as solar, water or wind. Let the sun shine in—The cheapest and most energy-efficient light and heat source is often right outside your windows. On {{U}} {{U}} 13 {{/U}} {{/U}}days, open blinds to let the sun light your home for free. Also remember that {{U}} {{U}} 14 {{/U}} {{/U}}entering a room equals passive solar heating. Even on cold winter days, sun streaming into a room can raise the temperature by several {{U}} {{U}} 15 {{/U}} {{/U}}.

单选题Up to now, the work has been easy.

单选题Poor children should not be Udeprived/U of the opportunity to participate in sports whenever possible.

单选题I catch a cold now and then .

单选题By the 1930s, the wolf had vanished from the American West.

单选题Desert perennials lose their leaves after the rainy season just as trees lose theirs in wetter climates before winter arrives, but the reasons for this feature are different.

单选题Eleven states, including the adjoining states of North and South Carolina, seceded from the United States in the 1860"s and formed a southern confederacy.

单选题 Mind-reading Machine A team of researchers in California has developed a way to predict what kinds of objects people are looking at by scanning what's happening in their brains. When you look at something, your eyes send a signal about that object to your brain. Different regions of the brain process the information your eyes send. Cells in your brain called neurons are responsible for this processing. The fMRI (functional Magnetic Resonance Imaging) brain scans could generally match electrical activity in the brain to the basic shape of a picture that someone was looking at. Like cells anywhere else in your body, active neurons use oxygen. Blood brings oxygen to the neurons, and the more active a neuron is, the more oxygen it will consume. The more active a region of the brain, the more active its neurons, and in turn, the more blood will travel to that region. And by using fMRI, scientists can visualize which parts of the brain receive more oxygen rich blood and therefore, which parts are working to process information. An fMRI machine is a device that scans the brain and measures changes in blood flow to the brain. The technology shows researchers how brain activity changes when a person thinks, looks at something, or carries out an activity like speaking or reading. By highlighting the areas of the brain at work when a person looks at different images, fMRI may help scientists determine specific patterns of brain activity associated with different kinds of images. The California researchers tested brain activity by having two volunteers view hundreds of pictures of everyday objects, like people, animals, and fruits. The scientists used an fMRI machine to record the volunteers' brain activity with each photograph they looked at. Different objects caused different regions of the volunteers' brains to light up on the scan, indicating activity. The scientists used this information to build a model to predict how the brain might respond to any image the eyes see. In a second test, the scientists asked the volunteers to look at 120 new pictures. Like before, their brains were scanned every time they looked at a new image. This time, the scientists used their model to match the fMRI scans to the image. For example, if a scan in the second test showed the same pattern of brain activity that was strongly, related to pictures of apples in the first test, their model would have predicted the volunteers were looking at apples.

单选题The theme of the second last paragraph is why the perennials can survive as plants for several years.

单选题We have to put up with her behavior. A. tolerate B. accept C. swallow D. take

单选题Lakes, Too, Feel Global Warming There's no doubt: In the last few decades, the average temperature on Earth has been higher than it has been in hundreds of years. Around the world, people are starting to measure the effects of global warming and trying to figure out what to do about it. Scientists recently used satellites to study the temperatures of lakes around the world, and they found that lakes are heating up. Between 1985 and 2009 , satellites recorded the nighttime temperatures of the surfaces of 167 lakes. During those 24 years, the lakes got warmer--by an average of about 0.045 degree Celsius per year. In some places, lakes have been warming by as much as 0.10 degree Celsius per year. At that rate, a lake may warm by a full degree Celsius in just 10 years. That difference may seem small--you might not even notice it in your bath. But in a lake, slightly warmer temperatures could mean more algae(水藻), and algae can make the lake poisonous to fish. The study shows that in some regions, lakes are warming faster than the air around them. This is important because scientists often use measurements of air temperature to study how Earth is warming. By using lake temperatures as well, scientists can get a better picture of global warming. The scientists say data on lakes give scientists a new way to measure the impact of climate change around the world. That's going to be useful, since no country is too big or too small to ignore climate change. Scientists aren't the only ones concerned. Everyone who lives on Earth is going to be affected by the rapid warming of the planet. Many world leaders believe we might be able to do something about it, especially by reducing the amount of greenhouse (温室) gases we put into the air. That's why the United Nations started the Framework Convention on Climate Change, or UNFCCC. Every year the convention meets, and representatives from countries around the world gather to talk about climate change and discuss global solutions to the challenges of a warming world.

单选题It is useless to argue with him once he has made up his mind .

单选题Ms Hawkins Uhandles/U the company's accounts.

单选题We explored the possibility of expansion at the conference.A. offeredB. includedC. investigatedD. accepted