Modern man has cleared the forests for farmland and for wood, and has also carelessly burned them. More than that, though, he has also interfered(干预) with the invisible bonds between the living things in the forests. There are many examples of this kind of destruction. The harmfulness of man's interference can be seen in what happened many years ago in the forest of the Kaibab plateau （凯亚巴布高原） of northern Arizona. Man tried to improve on the natural web of forest life and destroyed it instead.

    The Kaibab had a storybook forest of large-sized pine, Douglas fir, white fir, blue and Engelmann spruce. In 1882 a visitor noted, "We, who have wandered through its forests and parks, have come to regard it as the most enchanting（迷人的）region it has ever been our privilege to visit. "This was also the living place of the Rocky Mountain mule deer. Indians hunted there every autumn to gather meat and skins. The forest also had mountain lions, timber wolves and bobcats that kept the deer from multiplying too rapidly.

    Then, in 1906, President Theodore Roosevelt made the Kaibab a national game preserve. Deer hunting was forbidden. Government hunters started killing off the deer's enemies. In 25 years' time, 6,250 mountain lions, wolves and bobcats were killed. Before the program, there were about 4,000 deer in the Kaibab, by 1924, there were about 100,000.

    The deer ate every leaf and twig they could reach. But there was not nearly enough food. Hunting of deer was permitted again. This caused a slight decrease in the deer herd，but a far greater loss resulted from starvation and disease. Some 60 percent of the deer herd died in two winters. By 1930 the herd had dropped to 20,000 animals. By 1942 it was down to 8,000.

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。

    Bad news sells. If it bleeds, it leads. No news is good news, and good news is no news. Those are the classic rules for the evening broadcasts and the morning papers. But now that information is being spread and monitored(监控) in different ways, researchers are discovering new rules. By tracking people's e-mails and online posts, scientists have found that good news can spread faster and farther than disasters and sob stories.

    “The 'if it bleeds' rule works for mass media,” says Jonah Berger, a scholar at the University of Pennsylvania. “They want your eyeballs and don't care how you're feeling. But when you share a story with your friends, you care a lot more how they react. You don't want them to think of you as a Debbie Downer.”

    Researchers analyzing word-of-mouth communication—e-mails, Web posts and reviews, face-to-face conversations—found that it tended to be more positive than negative, but that didn't necessarily mean people preferred positive news. Was positive news shared more often simply because people experienced more good things than bad things? To test for that possibility, Dr. Berger looked at how people spread a particular set of news stories: thousands of articles on The New York Times' website. He and a Penn colleague analyzed the “most e-mailed” list for six months. One of his first findings was that articles in the science section were much more likely to make the list than non-science articles. He found that science amazed Times' readers and made them want to share this positive feeling with others.

    Readers also tended to share articles that were exciting or funny, or that inspired negative feelings like anger or anxiety, but not articles that left them merely sad. They needed to be aroused(激发) one way or the other, and they preferred good news to bad. The more positive an article, the more likely it was to be shared, as Dr. Berger explains in his new book, “Contagious: Why Things Catch On.”

    I remember the day when I first learned to ride a bike. It was a frightening, yet fun experience. My granddad was the one who taught me, and he helped me when I got hurt. The first time I got on a bike, I had no idea what I was doing, and just about everything went wrong. My granddad told me to just put my feet on the pedals and start, pedaling(骑自行车). He also told me he would hold onto the back of the bike the whole time, yet he didn't.

    As soon as I started trying to balance myself, he let go. I happened to look back just then.  I was scared to death that I was going to fall and hurt myself. When I was scared, my mind went blank from pedaling, and I just wanted off. I forgot how to use the brakes(车闸) and fell right off the bike. My granddad kept encouraging me to get up and try again, and after about 15 minutes, I finally stopped crying, got up and tried again.

    As soon as I started pedaling again, my pants got caught in the chain, and I fell flat on my face and hit my nose. Since that happened, my granddad decided to call it a day and try again the next morning. The next morning I woke up bright and early, and was very eager to try to ride my bike. My nose felt better, so I wasn't that afraid of falling anymore.

    Though I knew there were a lot of difficulties on the way to mastering the skills in riding a bike, l believed I could do well with my granddad's help. After all, riding a bike was what I wanted to do eagerly.

    It seems that you can hardly go to any bookstore without encountering Charles Dickens. From Oliver Twist to A Tale of Two Cites, Dickens' works still enjoy great popularity today and are placed on notable shelves.

    As someone who teaches Dickens, the question of why we still read him is often on my min. Nearly 10 years ago, I told my students that Dickens, works started crazes in Victorian readers. Then a hand shot up in the middle of the room. “But why should we still read his stuff?” A student asked. I was speechless because I had never considered the question myself. The answer I gave was only acceptable. “Because he teaches you how to think,” I said.

    The question annoyed me for years, and for years I told myself answers, but never with complete satisfaction. We read Dickens because he not only was a man of his own times, but also is a man for our times. We read Dickens because his exploration of the human mind is deep. We read Dickens because we can learn from the experiences of his characters. These are all wonderful reasons, but not exactly the reasons why I read Dickens.

    My search for an answer continued in vain, until one day a text message came from a student of mine. “We still read Dickens' novels,” she wrote, “because they tell us why we are what we are.” Simple as it was, that was the explanation I had thought for years.

    Like most people, I think I knew who I was without knowing it. I was Oliver Twist, always wanting and asking for more. I was Nicholas Nickleby, convinced that my father was watching me from beyond the grave. I was Pip, in love with someone far beyond my reach. I was all of these characters, and I began to understand more about why I was who I was because Dickens had told me so much about human beings. Dickens shines a light on who we are during the best and worst of times. That's why we still need to read him today.

    The world's insects are going down the path of extinction, threatening a "catastrophic collapse of nature's ecosystems", according to the first global scientific review. More than 40％of insect species are declining and third are endangered, the analysis found. The rate of extinction is eight times faster than that of mammals, birds and reptiles.

    "It should be of huge concern to all of us, for insects are at the heart of every food web. They pollinate (授粉) the large majority of plant species, keep the soil healthy, recycle nutrients, control pests, and much more. Love them or 1oathe them, we humans cannot survive without insects, "said Prof Dave Goulson at the University of Sussex in the UK.

    The analysis, published in the journal Biological Conservation, says intensive (集约型) agriculture is the main driver of the declines, particularly the heavy use of pesticides. Urbanisation and climate change are also significant factors.

    "If insect species losses cannot be stopped, this will have catastrophic consequences for both the planet's ecosystems and for the survival of mankind. It is very rapid. In 10 years you will have a quarter less, in 50 years only half left and in 100 years you will have none," said review author Francisco Sánchez-Bayo, at the University of Sydney, Australia.

    One of the biggest impacts of insect loss is on many birds, reptiles, amphibians and fish that eat insects. "If this food source is taken away, all these animals starve to death," he said. Such effects have already been seen in Puerto Rico, where a recent study revealed a 98％fall in ground insects over 35 years.

    Matt Shardlow, at the conservation charity Buglife, said: "It is thoughtful to see this evidence that shows the pitiful state of the world's insect populations. It is increasingly obvious that the planet's ecology is breaking and there is a need for a strong and global effort to prevent and change these terrible trends."

    It is every kid's worst nightmare(噩梦) and six-year-old Jaden Hayes has lived it twice. First he lost his dad when he was only at the age of four and then last month his mom died unexpectedly in her deep sleep.

    "I tried and I tried and I tried to get her awake, but... I just couldn't," said Jaden.

    No one could imagine how heartbroken Jaden was.

    But there's another side to his sadness. A side he first made public a few weeks ago when he told his aunt, Barbara DiCola, and now his guardian(监护人)after both his parents died, that he was sick and tired of seeing everyone sad all the time. And he had a plan to fix it.

    "And that was the beginning of it," said Barbara. "That's where the adventure began."

    Jaden asked his aunt Barbara to buy a bunch of little toys and bring him to downtown Savannah, Georgia near where he lives, so he could give them away to anyone who will smile to him. "I'm trying to make people smile," said Jaden.

    Jaden targets people who aren't already smiling and then turns their day around. He's gone out on four different occasions now and he is always successful. Even if sometimes he doesn't get exactly the reaction he was hoping for.

    It is just so overwhelming to some people that a six-year-old orphan would give away a toy -- expecting nothing in return -- except a smile.

    "I'm depending on it to be 33, 000," said Jaden. When asked if he thinks he can make that goal, he answered: "I think I can."