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

单选题Certainly no creature in the sea is odder than the common sea cucumber(海参). All living creatures, especially human beings, have their peculiarities, but everything about the little sea cucumber seems unusual. What else can be said about an odd animal that, among other eccentricities, eats mud, feeds almost continuously day and night but can live without eating for long periods, and can be poisonous hut is considered supremely edible by gourmets(美食家) ? For some fifty million years, despite all its eccentricities, the sea cucumber has subsisted on its diet of mud. It is adaptable enough to live attached to rocks by its tube feet, under rocks in shallow water, or on the surface of mud fiats. Common in cool water on both Atlantic and Pacific shores, it has the ability to suck up .mud or sand and digest whatever nutrients are present. Sea cucumbers come in a variety of colors, ranging from black to reddish-brown to sandcolor and nearly white. One form even had vivid purple tentacles. Usually the creatures are cucumbers-shaped——hence their name——and because they are typically rock inhabitants, this shape, combined with flexibility, enables them to squeeze into narrow cracks where they are safe from predators and ocean currents. Although they have voracious appetites, eating day and night, sea cucumbers have the capacity to become inactive and live at a low metabolic rate feeding sparingly or not at all for long periods, so that the marine organisms that provide their food have a chance to multiply. If it were not for this faculty, they would devour all the food available in a short time and would probably starve themselves out' of existence. But the most spectacular thing about the sea cucumber is the way it defends itself. Its major enemies are fish and crabs, when attacked, it squirts all its internal organs into the water. It also casts off attached structures such as tentacles. The sea cucumber will eviscerate排除内脏) and regenerate itself if it is attacked or even touched; it will do the same if the surrounding water temperature is too high or if the water becomes too polluted.

单选题Stage Fright Fall down as you come onstage. That"s an odd trick. Not recommended. But it saved the pianist Vladimir Feltsman when he was a teenager back in Moscow. The veteran cellist (大提琴演奏家) Mstislav Rostropovieh tripped him purposely to cure him of pre-performance panic. Mr. Feltsman said, "All my fright was gone. I already fell. What else could happen?" Today, music schools are addressing the problem of anxiety in classes that deal with performance techniques and career preparation. There are a variety of strategies that musicians can learn to fight stage fright and its symptoms: icy fingers, shaky limbs, racing heart, blank mind. Teachers and psychologists offer wide-ranging advice, from basics like learning pieces inside out, to mental discipline, such as visualizing a performance and taking steps to relax. Don"t deny that you"re jittery (紧张不安的), they urge; some excitement is natural, even necessary for dynamic playing. And play in public often, simply for the experience. Psychotherapist Diane Nichols suggests some strategies for the moments before performance, "Take two deep abdominal breaths, open up your shoulders, then smile," she says. "And not one of these "please don"t kill me" smiles. Then choose three friendly faces in the audience, people you would communicate with and make music to, and make eye contact with them." She doesn"t want performers to think of the audience as a judge. Extreme demands by mentors or parents are often at the root of stage fright, says Dorothy Delay, a well-known violin teacher. She tells other teachers to demand only what their students are able to achieve. When Lynn Harrell was 20, he became the principal cellist of the Cleverland Orchestra, and he suffered extreme stage fright. "There were times when I got so nervous. I was sure the audience could see my chest responding to the throbbing. It was just total panic. I came to a point where I thought, "If I have to go through this to play music, I think I"m going to look for another job."" Recovery, he said, involved developing humility-recognizing that whatever his talent, he was fallible, and that an imperfect concert was not a disaster. It is not only young artists who suffer, of course. The legendary pianist Vladimir Horowitz"s nerves were famous. The great tenor Franco Corelli is another example. "They had to push him on stage," Soprano Renata Scotto recalled. Actually, success can make things worse. "In the beginning of your career, when you"re scared to death, nobody knows who you are, and they don"t have any expectations," Soprano June Anderson said. "There"s less to lose. Later on, when you"re known, people are coming to see you, and they have certain expectations. You have a lot to lose." Anderson added, "I never stop being nervous until I"ve sung my last note."

单选题As soon as we crossed the border, enemy troops started {{U}}firing{{/U}} at our troops.

单选题Mr. Bill has never been to China. {{U}}As a result{{/U}} he knows little about this country.

单选题Greene spent a brief time at Cambridge.A. hardB. goodC. shortD. long

单选题A dark suit ismore suitable for the evening party.A. favorableB. suitableC. preferableD. proper

单选题I remember lots of things. A．much B．large C．big D．many

单选题We need to extract the relevant financial data.A. storeB. saveC. obtainD. review

单选题He was a very smart boy but he made a foolish decision this time.A. cleverB. sillyC. braveD. shy

单选题I don"t quite follow what she is saying.

单选题We should not sacrifice environmental protections to foster economic growth. A．reduce B．promote C．realize D．give