With global warming and melting ice, it isn't easy being a polar bear anymore. Some studies have predicted that polar bears could die out by the end of the century. The good news is not all researchers think the bears are absolutely disappearing. Scientists at the American Museum of Natural History(AMNH) have published a new paper indicating that things might not be as bad for polar bears as some scientists expect.

To understand the reason for the researchers' cautious optimism, we must first understand the factors that are threatening the polar bear's existence. Polar bears consume a diet of mainly young seals. In order to hunt these seals, polar bears need to rest at the top of sea ice—the same ice that is increasingly melting for most of the year thanks to climate change. In another 50 years, experts expect that the Arctic will be too warm for sea ice to form for half of the year, leaving polar bears without a reliable food source and in serious danger of starvation.

As it turns out, alternative food sources for the polar bears aren't completely out of the question. For as long as biologists have tailed after the animals, they've seen polar bears eating animals found on land like caribou(驯鹿) and snow geese—as well as the snow geese's eggs.

    Can polar bears actually survive off these alternative food sources for long periods of time? To figure this out, researchers calculated the nutrients that a caribou and snow geese diet would provide. They found that even adult male polar bears would be able to obtain more calories than would burn in hunting these meals. Moreover, the food would provide the food lecessary to avoid starvation during the summer months.

    Unfortunately, not all polar bears have tended to seek food on land. That said, the researchers expect that necessity would push more polar bears to hunt on land to avoid starvation. They also expect that the bears could learn from their fellow bears how to hunt on land until the practice becomes second nature.

    While contact between adolescents (between the ages of fifteen and nineteen) and their peers (同龄人) is a universal characteristic of all cultures, the nature and the degree of such contact vary a great deal. In American contemporary society, adolescents spend much more time with their peers than with younger children or adults.

    This pattern of age segregation(隔离) in American society did not become usual until the beginning of the industrialized society. Changes in the workplace separated children from adults, with adults working and children attending school. The dramatic increase of mothers in the workplace has further contributed to the reduction in the amount of time adolescents spend with adults. School reform efforts during the nineteenth century, which resulted in age-segregated schools and grades, have reduced the amount of time adolescents spend with younger children. Finally, the changes in population are considered a factor that may have contributed to the emergence of adolescent peer culture. From 1955 t0 1975, the adolescent population increased dramatically, from 11 percent t0 20.9 percent. This increase in the number of adolescents might be a contributing factor to the increase in adolescent peer culture in terms of growth in size.

    Research supports the view that adolescents spend a great deal of time with their peers. Reed Larson and his colleagues examined adolescents' daily activities and found that they spend more time talking to their friends than engaging in any other activity. In a typical week, high school students will spend twice as much time with their peers as with adults. This gradual withdrawal from adults begins in early adolescence. In sixth grade, adults (excluding parents) account for only 25 percent of adolescent social networks. Another important characteristic of  adolescent peer culture is its increasingly autonomous (白治的) function. While childhood peer groups are conducted under the close supervision of parents, adolescent peer groups typically make an effort to escape adult supervision and usually succeed in doing so.

    (Note: Answer the questions or complete the statements in NO MORE THAN EIGHT WORDS.)

    [1]Stamp collectors usually collect stamps only from certain countries or regions. The traditional method of stamp collecting is to organize stamp collection according to the issue dates.

     [2]Of course, there are many    .  . You can collect stamps relating to a particular theme. For example, sport lovers may choose the Olympic theme. They try their best to find Olympic stamps issued by various parts of the world every four years. Some of them may want to concentrate on even more specific sport activities like ball games, gymnasium, swimming, etc.

     [3]If you like astronomy, you may be keen on collecting stamps describing the stars, planets, spacecraft, spacemen, etc. once you have fixed the topic, you no longer need to bother about stamps other than the theme you selected. Then, you can put all your effort to collect the stamps around it.

     [4]China issues zodiac animal stamps (十二生肖邮票) every year to celebrate the Lunar New Year. They are extremely popular and a lot of collectors wait patiently for 12 years to collect a full set of them. Hong Kong's Lunar New Year special stamp series began in 2000 with the Year of Dragon and the twelfth and final set was issued in 2011, the Year of Rabbit. Recently some Western countries have issued zodiac animal stamps, which attract a lot of attention as well.

     [5]You may choose any theme you like. However, you should bear in mind an essential point. The topic you choose should not be too narrow. Otherwise, it is very difficult to accumulate stamps around the topic. You will be depressed and even lose your interest in collecting stamps.

      [6]Collecting stamps with themes is especially popular among teenagers because there is a wide range of choices for them. The main challenge is how you organize and expand your collection around your theme.

    When my father was celebrating a milestone (里程碑) birthday, I pulled together a surprise gift that he would never forget.

    As he was approaching 60,1 had a firm idea: What if I could get the memories people had of him, put each one into an envelope - 60 in total - and have him open them, one by one, on his birthday? So I wrote an e-mail to family and friends, explaining my idea.

    I sent the e-mail and waited. And then the replies started coming in and I was very, very surprised. There were so many memories, and they were all so lovely. They came from the '50s, '60s, '70s, from every decade（十年） between now and the day my dad was born. They came from my mother, my siblings, my grandma, my dad's friends from high school, his sister, my dad's first boss, a colleague at his first job, from people who hadn't seen my dad in 40 years, from people I myself hadn't even informed. They typed them and handwrote them. They mailed them and e-mailed them.

    The night before Dad's birthday, my sister and 1 stayed up late, putting everything together with some

    The next morning, after breakfast and presents and cake, we gave the pile of envelopes to him. "Just one more thing for you," we said.

It took him a long time to open them and read. Each one was a brief ticket to another time, a leap (跳跃) backward over years and decades. There was a lot of laughter and a few tears, too.

    I was kind of sad when the project was over because it was great fun to collect these memories. It gave me a different picture of my dad.

    It was a hot summer day that found me running down the street with a dollar in my sweaty hand. The closer I got to Sam & Joe's Stationery Store, the more excited I was. After all, a dollar was a tidy sum for an 11-year-old boy in 1961.

    Out of breath, I swung open the door and got a blast of cold air that instantly cooled me off. I was in a place of pure happiness. Sam & Joe's had it all—books, candy, toys, baseball cards，puzzles and games. I went directly to the bar and ordered a bottle of soda. There I sat, considering my next move.

    Books always came first. I picked out five titles. Next came the candy, rows and rows of it. I chose five candy bars, which brought my total to 75 cents. Then a bottle of cold orange juice, a bag of chips and a pack of Ted Williams baseball cards. After paying the clerk, I still had 5 cents.

    I hurried directly to my backyard, where an apple tree patiently waited for me. There, sitting in the shade against its strong trunk, I read my books, ate my candy and drank my orange juice.

    As I sat in my own personal heaven, I started thinking about having more. That's when a fantastic life—changing idea popped into head: If I could get more money, I could buy more books I liked, buy anything I wanted. That's how it all started.

    About 7 million people over the age of 65 have been diagnosed with depression, and many more could be suffering. It is high time that you learned how to know the signs and help them. Depression is a big problem for seniors, especially those who are lack of care and attention. Older people are much more likely to be alone, socially isolated(孤立的) or feel a lack of purpose. Sometimes older people have a much more difficulty time admitting mental health problems. Many times, the link between depression and physical illness is much stronger.

    The elderly don't like to express sadness the way that young people do. Older people who are depressed may have more physical troubles and may pay more attention to them. Depression may result from early memory loss and meanwhile, depression will make a person forget more and faster. A patient with early memory loss and depression really needs to be treated for the depression to slow the memory loss. A mood change is also a sign of depression. If a previously calm person becomes increasingly annoyed, or a previously clean person no longer bothers to shower or clean up, that person should be considered.

Don't tell older adults that you think they may be depressed, as older adults — particularly men–see depression as a weakness. What you should do is tell them you're worried about their health. Tell them they seem to be out of sorts.

    Say you just want to check with the doctor to see what's going on. Once you've used physical symptoms to get that person to agree to a check-up, mention your fear to the doctor and allow the doctor to approach the subject of depression with the patient.