On May 23, 1989, Stefania Follini came out from a cave at Carlsbad, New Mexico. She hadn't seen the sun for eighteen and a half weeks. Stefania was in a research program, and the scientists in the program were studying body rhythms. In this experiment Stefania had spent 130days in a cave, 30 feet in depth.

    During her time in the cave, Stefania had been completely alone except for two white mice. Her living place had been very comfortable, but there had been nothing to tell her the time. She'd had no clocks or watches, no television or radio. There had been no natural light and the temperature had always been kept at 21℃.

    The results were very interesting. Stefania had been in the cave for over four months, but she thought she had been there for only two. Her body clock had changed. She hadn't kept to a 24-hour day, she had stayed awake for 20～25 hours and then had slept for 10 hours. She had eaten fewer meals and had lost 171bs in weight as a result! She had also become rather depressed.

    How had she spent her time in the cave? As part of the experiment she'd done some physical and mental tests. She'd recorded her daily activities and the results of the tests on a computer. This computer had been specially programmed for the project. Whenever she was free, she'd played cards, read books and listened to music. She'd also learned French from tapes.

    The experiment showed that our body clocks are affected by light and temperature. For example， the pattern of day and night makes us wake up and go to sleep. However, people are affected in different ways. Some people wake up naturally at 5:00 a.m., but others don't start to wake up till 9:00 or 10:00 a.m. This affects the whole daily rhythm. As a result the early risers are at their best in the late morning. The late risers, on the other hand, are tired during the day and only come to life in the afternoon or evening!

根据短文内容，选择最佳答案，并将选定答案的字母标号填在题前括号内。

    One of the most important things in the world is friendship. In order to have friends, you have to be a friend. But how can you be a good friend at school?

    Listen — Listen when they are talking. Don't say anything unless they ask you a question. Sometimes it's not necessary for you to have anything to say; they just need someone to talk to about their feelings.

    Help them — If your friend is ever in need of something, be there to help them. You should try to put them first, but make sure you don't do everything they want you to do. Try to take an extra (额外的) pencil or pen with you to classes in case (以防) they forget one. Have a little extra money in your pocket in case they forget something they need.

    Be there for them — Try to make something for your friend to help make them feel better in hard times. Making cards and encouraging them are among the nicest things you can do for a friend. Marilyn Monroe, a famous U.S. actor, once said, “I often make mistakes. Sometimes I am out of control. But if you can't stay with me at my worst, you are sure not to deserve (值得) to be with me at my best.” Always remember this! If you don't want to stay with your friends when they're in hard times, then you don't deserve to be with them when they're having a good time!

    Try to make plans with your friends. Go shopping, go for ice cream, have a party, go to a movie and so on. Take time to know each other even better by doing something you both enjoy. By planning things together, you both can have a good time. And you'll remember these things when you're all old!

    The past two decades have seen astronomers' catalogue of planets expand over two hundred times, as new techniques and better telescopes have found more than 2,000 of them orbiting stars other than the sun. But in the solar system itself, the list of planets has actually shrunk, Pluto（冥王星）having been downgraded from that status in 2006. The number of the sun's planetary companions has thus fallen from nine to eight.

    Now, a pair of astronomers from the California Institute of Technology think they have evidence that will restore the sun's record to its previous value. Their analysis of objects orbiting in the Kuiper Belt（柯伊伯带）, a ring of frozen asteroids（小行星）that circle beyond the orbit of Neptune (and of which Pluto is now regarded as the largest member), suggests to them that something about ten times as massive as Earth has changed those orbits. If you knew where to look, this planet-sized object would be visible through a suitable telescope. And Konstanin Batygin and Michael Brown believe they do know.

As they write in the Astronomical journal, they have analyzed the orbits of Kuiper Belt objects and found six that behave in a peculiar way. As the diagram shows, the points of closest approach of these objects to the sun, known as their perihelia（近日点）, almost coincide. Moreover, these perihelia all lie near the ecliptic（黄道）—the plane of Earth's orbit and also, approximately, that of the other planets—while the objects' orbits are all angled at 30° below the ecliptic. The chance of all this being a coincidence, the two researchers estimate, is about seven in 100,000. If it is not a coincidence, it suggests the six objects have been guided into their orbits by the gravitational intervention of something much larger.

    A computer analysis Dr Batygin and Dr Brown performed suggests this something is a planet weighing 5-15 times as much as Earth, whose perihelion is on the opposite side of the sun from the cluster, and which thus orbits mainly on the other side of the solar system from the objects its orbit has affected. This planet's perihelion would be 200 times farther from the sun than Earth's, and the far end of its orbit might be as much as six times that distance away. This gives a search zone, and Dr Batygin and Dr Brown are using Subaru, a Japanese telescope, to perform that search.

    Given other demands on Subaru's time, it might take five years for this search to find (or not find) the hypothetical planet. But looking at some existing data from. The Widefield Infrared Survey Explore, a satellite, might also show it, if it is there to be seen.

    Ironically, it was Dr Brown as much as anyone who was responsible for Pluto's downgrading, for he discovered Eris, an object almost as big as Pluto, in 2005.

    That discovery did much to damage Pluto's planetary proof. By his own admission, he was skeptical that the anomalies he and Dr Batygin have investigated actually would point to the existence of a replacement ninth planet. He is a skeptic no longer. Whether he is actually right may soon become apparent.

    Two friends have an argument that breaks up their friendship forever, even though neither one can remember how the whole thing got started. Such sad events happen over and over in high schools across the country. In fact, according to an official report on youth violence, “In our country today, the greatest threat to the lives of children and adolescents is not disease or starvation or abandonment, but the terrible reality of violence”. Given that this is the case, why aren't students taught to manage conflict the way they are taught to solve math problems, drive cars, or stay physically fit?

    First of all, students need to realize that conflict is unavoidable. A report on violence among middle school and high school students indicates that most violent incidents between students begin with a relatively minor insult (侮辱). For example, a fight could start over the fact that one student eats a peanut butter sandwich each lunchtime. Laughter over the sandwich can lead to insults, which in turn can lead to violence. The problem isn't in the sandwich, but in the way students deal with the conflict.

    Once students recognize that conflict is unavoidable, they can practice the golden rule of conflict resolution ( 解决): stay calm. Once the student feels calmer, he or she should choose words that will calm the other person down as well. Rude words, name-calling, and accusations only add fuel to the emotional fire. On the other hand, soft words spoken at a normal sound level can put out the fire before it explodes out of control.

    After both sides have calmed down, they can use another key strategy ( 策略) for conflict resolution: listening. Listening allows the two sides to understand each other. One person should describe his or her side, and the other person should listen without interrupting. Afterward, the listener can ask non-threatening questions to clarify the speaker's position. Then the two people should change roles.

    Finally, students need to consider what they are bearing. This doesn't mean trying to figure out what's wrong with the other person. It means understanding what the real issue is and what both sides are trying to accomplish. For example, a shouting match over a peanut butter sandwich might happen because one person thinks the other person is unwilling to try new things. Students need to ask themselves questions such as these：How did this start? What do I really want? What am I afraid of? As the issue becomes clearer, the conflict often simply becomes smaller. Even if it doesn't, careful thought helps both sides figure out a mutual（彼此共同的） solution.

    There will always be conflict in schools, but that doesn't mean there needs to be violence. After students in Atlanta started a conflict resolution program, according to Educators for Social Responsibility, “64 percent of the teachers reported less physical violence in the classroom; 75 percent of the teachers reported an increase in student cooperation; and 92 percent of the students felt better about themselves”. Learning to resolve conflicts can help students deal with friends, teachers, parents, bosses, and coworkers. In that way, conflict resolution is a basic life skill that should be taught in schools across the country.

    Alaska Airlines has the cheapest fares around, but you receive superb service unequal to its price. In case you don't know, Alaska Airlines does not just go to Alaska, but includes states such as Washington, California, and Hawaii. Our prices are reasonable and we offer great service.

    Alaska Airlines is generous. For each bag you check in, it must weigh 50 pounds or less, which is extremely generous for domestic flights. Your baggage is allowed to be up to 62 inches in length. You're also allowed one carry-on bag in addition to one personal item which can be a purse, a laptop computer, or a briefcase.

    Not only do we give you the cheapest airfare, but we offer you a visa card which you can earn plenty of miles on. Upon approval, you will receive 25,000 Bonus Miles. From then on, for each dollar you charge to this card, you will receive 3 miles and there's no limit to the amount of miles you can earn. You also receive a $99 round-trip discount code for a Companion Ticket each year for using this card. This is a sweet deal and very generous. Think about all of your purchases you make during the month. Now multiply that by three. You're talking about a free trip cross country in just a few short months. Wow!

    Alaska Airlines receives great reviews for its performance, punctuality, and professional service. In addition to its great reviews from customers, Alaska Airlines has received lots of awards and recognitions. Network Carriers in North America has rated Alaska Airlines for the highest in customer satisfaction for the past 4 years. We have also received the Executive Travel's leading edge Award. We were also named on the 2011 Washington Green 50 list.

    Alaska Airlines is quickly gaining the recognition it deserves. We're adding higher expectations to the flying experience. Try it out.

    Science Advances published a new research report, saying bees are capable of addition and subtraction (减法)in Arithmetic(算术) learning—using colors in the place of plus and minus symbols.

    It isn't unusual to see the ability to count—or at least distinguish between differing quantities in the animal kingdom—Such ability has been seen in frogs, spiders, and even fish. But solving equations (方程式) using symbols is rare, so far only achieved by famously brainy animals such as chimpanzees. The previous research says the social insects, ants, can count to four and understand the concept of zero and researchers wanted to test the limits of what their tiny brains can do.

    The experiment goes like this. Scientists trained 14 bees to link the colors blue and yellow to addition and subtraction, respectively. They put the bees at the entrance of a Y-shaped maze (迷宫), where they were shown several shapes in either yellow or blue. If the shapes were blue, bees got a reward if they went to the end of the maze with one more blue shape (the other end had one less blue shape); if the shapes were yellow, they got a reward if they went to the end of the maze with one less yellow shape.

    The testing worked the same way: Bees that "subtracted" one shape when they saw yellow, or "added" one shape when they saw blue were considered to have aced the test. The bees got the right answer 63% to 72% of the time, depending on the type of equation and the direction of the right answer—much better than random guesses would allow.

    While the results came from just 14 bees, researchers say the advance is exciting. If a brain about 20,000 times smaller than ours can perform maths using symbols, it could pave the way to novel methods in artificial intelligence (AI) and machine learning. Just don't ask the bees to do your homework anytime soon.