A student was one day taking a walk with his teacher. As they went along, they saw a pair of old shoes lying in the path. They were a poor farmer's, who was working in the nearby field.

    The student turned to the teacher, saying: “we will hide his shoes, and hide ourselves behind those trees, and wait to see what he will do.”

    “My young friend,” answered the teacher, “we should never make fun of the poor. Why not put a coin in each shoe, and then we will hide ourselves and watch?” The student did so and they both hid themselves behind the trees. The poor man soon finished his work, and came across the field to the path where he had left his coat and shoes.

    After putting on his coat, he put his foot into one of his shoes, and felt something hard. Then he bent(弯腰) down to feel what it was, and found the coin. Surprised, he looked at the coin, turned it around and looked at it again. He then looked around, but no person was seen. He put the money into his pocket, and continued to put on the other shoe. His surprise was doubled on finding the other coin.

    He couldn't control his feelings and fell to his knees, looked up to the sky and expressed his thanks. Then he spoke of his wife, sick and helpless, and his children without bread. He said the help would save them from dying.

    The student stood there deeply moved, and his eyes were filled with tears. “Now,” said the teacher, “Are you not much happier than if you had hidden the shoes?”

    In the United States 30 percent of the adult population has a “weight problem”. To many people, the cause is clear: We eat too much. But scientific evidence does little to support this idea. Going back to the America of 1910, we find that people were thinner than today, yet they ate more food. In those days people worked harder physically（体力地）, walked more, used machines much less, and didn't watch television.

    Several modern studies, moreover, have shown that fatter people don't eat more on average（平均）than thinner people. In fact, some investigations, such as a 1970 study of 3,545 London office workers, report that, on balance, fatter people eat less than slimmer people.

    Studies show that slim people are more active than fat people. A study by a research group at Stanford University School of Medicine found the following interesting facts.

    The more the men ran, the greater loss of body fat.

    The more they ran, the greater their increase in food intake（吸收）.

    Thus those who ran the most ate the most, yet lost greatest amount of body fat.

    Some of the world's most significant problems never hit headlines. One example comes from agriculture. Food riots（暴动）and hunger make news. But the trend lying behind these matters is rarely talked about. This is the decrease in the growth in production of some of the world's major crops. A new study by the University of Minnesota and McGill University in Montreal looks at where, and how far, this decline is occurring.

    The authors take a vast number of data points for the four most important crops: rice, wheat, corn and soyabeans. They find that on between 24% and 39% of all harvested areas, the improvement inproduction that took place before the 1980s slowed down in the 1990s and 2000s.

    There are two worrying features of the slowdown. One is that it has been particularly sharp in the world's most populous countries, India and China. Their ability to feed themselves has been an important source of relative stability both within the countries and on world food markets. That self-sufficiency (自给自足) cannot be taken for granted if productions continue to slow down.

    Second, production growth has been lower in wheat and rice than in corn and soyabeans. This is problematic because wheat and rice are more important as foods, accounting for around half of all calories consumed. Corn and soyabeans are more important as feed grains. The authors note that "we have preferentially focused our crop improvement efforts on feeding animals and cars rather than on crops that feed people and are the basis of food security in much of the world."

    The report also states the more optimistic findings of another new paper which suggests that the world will not have to dig up a lot more land for farming in order to feed 9 billion people in 2050, as the Food and Agriculture Organisation has argued.

    Instead, it says, thanks to slowing population growth, land currently ploughed（犁）up for crops might be able to revert (回返) to forest or wilderness. This could happen. The trouble is that the prediction assumes continued improvements in productions, which may not actually happen.

    Have you ever awakened and felt like you couldn't move? If so, it probably scared you. You may have thought something terrible had happened to you. Actually, many people have this experience on a regular basis. It is called sleep paralysis. Although it sounds scary, it is normal.

    Sleep paralysis happens when a person is falling asleep or waking up. As the person falls asleep, his or her body slowly relaxes. Usually the person's mind relaxes at the same time, but occasionally the mind stays awake longer than the body. As a result, the person can be conscious, or aware, but have trouble moving or speaking. Sleep paralysis can also occur as you wake up. Fortunately, the condition rarely lasts for more than a few seconds. Movement and speech soon return to normal.

    Some people report unusual experiences during sleep paralysis. They may hear, see, or feel things that don't exist. At one time, people thought that ghosts or monsters had entered the room and were holding them down, keeping them from moving. Science has helped us understand that such visions are actually a part of sleep paralysis. Now we know that getting too little sleep, taking certain medications, and changing your sleep schedule can cause sleep paralysis. This condition can be scary if you, but it's just a trick that your mind is playing on your body.

    King's College Summer School is a training program every year for high school students at all levels who want to improve their English. Courses are given by the teachers of King's College and other colleges in New York. Trips to museums and culture centers are also organized. This year's summer school will be from July 25 to August 15.

    More information is as follows:

    Wolves strike fear into the hearts of many species, humans included. Our fear of them has brought them to the edge of dying out, as we have cruelly killed them as competitors and trouble-makers. But researchers are discovering that the very fear they put into prey（被捕食者）species is exactly what helps make ecosystems（生态）healthy.

    Yellowstone National Park is a typical example of just how wolves can help repair an ecosystem. An October 2018 study analyzed 40 years of research on large animals inside the park.

    "Yellowstone has benefited from the reintroduction of wolves in ways that we did not anticipate, especially the complexity of biological interactions（互动） in the park," explained Mark Boyce, a professor in the Department of Biological Sciences." We were really surprised at that and we'd never have seen these responses if the park hadn't adopted ecological-process management—allowing natural ecological processes to take place with least human intervention."

    After the wolves were re-introduced at Yellowstone, willow and cottonwood trees increased in number. The population of bears and bison also rose and what was once a ruling deer-wolf interaction is now more diverse.

    To learn more about just how wolves are beneficial, a short documentary from Quest explains how the presence of wolves influences the behavior of deer, which eventually makes entire ecosystems more biologically diverse and healthy. In this documentary, biologist Aaron Wirsing explored why wolves and other top predators （捕食者）were needed for diverse ecosystems to develop. Using a simple video camera, Wirsing is gaining a unique view point on predator-prey relationships and changing the way we think about wolves.

    The research is one more piece of evidence for why protecting these top predators is important not just for wolves as a species, but for hundreds of species at every level of an ecosystem. The fear they bring along may be the very angle that helps save them from dying out.