John and Jack met at the old bench every afternoon. Then they played football. But they didn't have enough money to buy a real football. So Jack made a ball out of old socks covered with a piece of plastic. Every time, the two friends didn't stop kicking and running until very late.

    On Monday afternoon, John and Jack met again at the old bench. Soon the home-made ball was running across the grass. The boys laughed and shouted happily. The ball was stopped by a boy wearing a nice pair of sports shoes. John was upset when he saw it was Steven.

    The next morning, John's mother gave him a bill. “Your uncle sent you a birthday present.”She smiled. John's eyes grew big when he saw the ＄100 bill. Later that day, his mother bought a pair of new sports shoes and a real football.

    That afternoon Steven invited John to play football. Steven did not want Jack to join them only because Jack's sports shoes were dirty. When the game was over, John and Steven walked past the old bench where Jack was sitting. Steven picked up a stone and threw it at him. John, holding his new football in his hands, walked on and did not look back.

    Several days later, as John walked past the old bench, he saw something lying under it. He looked closer and saw it was the home-made ball. John was full of sadness when he saw the ball. As his sadness turned to anger, he picked up his new football and kicked it into the air. Then he walked to the beach, sat down and waited.

    In today's world of modern science and medicine, a more traditional treatment is once again becoming popular -- animal friendship.

    It is now well-known that people with problems such as heart disease or cancer live longer and get better more quickly if they have pets. Keeping pets lowers blood pressure and makes people less worried. Animals are increasingly important in treating older people who have memory loss(损失) and other brain problems. These people often feel nervous and upset. Activities with animals help them improve their physical condition and also give them joy, entertainment and loving friendship.

    Here is a case that shows the benefits of animals. John was a six-year-old boy. He had no physical problems. He just refused to talk. His older cousin, Ned, had a parrot called Sally, and John used to visit it. When he arrived, Net used to say, “Hi, John!” We all know parrots copy what they hear. After a few visits, Sally began saying “Hi, John!” When John came into the room. Then, one day, John turned to the parrot and replied “Hi, Sally!” Staying with the parrot encouraged John to begin talking.

    Another use of animal helpers is in schools. In some cases, they are used to teach children to get on and share with others, and even to teach them about animals.

    If you want to know more about animal helper programs, you can get in touch with organizations like Riding for the Disabled or do a search about animals on the Internet. You don't have to be an animal trainer or a doctor to join in.

根据短文内容选择最佳答案。

    Both seasonal flu, a disease like a very bad cold, and much larger pandemics, like the one caused by H7N9（禽流感） in 2013, are the result of a race between the flu virus  and the immune system which can protect people from illness. Here's how it works.

    Viruses, which cause pandemics, have two important proteins "haemagglutinin(H) and neuraminidase(N).H helps the virus go into a cell .N helps new virus break out of that cell .They are parts of a virus that may be known and dealt with by the immune system

    A flu virus attacks a host cell in order to reproduce itself. But the virus created out of it is quite different now. The virus's genetic material is copied with low fidelity. That difference produces virus which immune system does not always know and deal with immediately. Each year's seasonal virus is therefore a little bit different, and thus requires an updated vaccine to prevent people from getting that disease.

    Pandemics viruses have bigger changes in this process .Many hosts' defences are unprepared for such big changes, which happen three or four times a century .The 1918 pandemics was caused by viruses carrying H1 and N1.Anotber two pandemics in 1957 and 1968 were caused by viruses carrying H2and H3 together with N2.They are numbered by scientists. Much of this change goes on outside humans. A flu is usually from sick binds. Sometimes a bird-flu appears with materiel that enable it to spread among people .The H7N9 is recently worrying scientists in the health center.

    The flu virus sometimes jumps directly from a bird(often a chicken) to a person, but more usually passes through a pig The cells in bird and human are built differently, It means us that the virus needs different sets of material to attack them .Pig cells have features of both so that it can act as a platform in which the virus can fit from one to the other .Even after it has made humans ill, a virus cannot go ca to cause a pandemic unless it also gets the ability to pus easily between people, Luckily, this is something H7N9 has yet to do.

    Do you think laughter can help you deal with pain? Scientists from Britain did two experiments(实验). The first was done in a lab. People wore special wristbands(腕带). Some of them were asked to watch comedies while others watched serious programs. Then the scientists tightened(勒紧)the wristbands to see how much pain the people could feel.

    The other test was done at an art festival. Some people watched a comedy show and others watched a drama(戏剧). At the same time, they had to put their backs against the wall and keep their legs bent(弯曲的)just like sitting on a chair. They did this before and after the show.

Scientists found that just 15 minutes of laughter improves people's ability to stand pain by 10%. However, the serious programs and the drama didn't make a difference to pain at all.

    The study found that the magic power of laughter comes from endorphins(内啡肽). These are chemicals(化学物质). They are produced by the human body. They make you feel less pain and can make people feel happier. Exercise can produce endorphins. Your muscles(肌肉)move in and out when you are laughing. Scientists believe that this makes your muscles tiring, so we start to produce endorphins.

    Scientists also found that the only real and relaxing laughter works not just polite laughter.

    Next time you have a headache, get together with a group of Mends, watch a funny movie and laugh. You will soon feel a lot better because laughter is the best medicine.