People who do not get enough vitamin A in their diet may develop night blindness. But in the developing world, a lack of vitamin A causes much more serious harm to children. The world Health Organization links the lack of vitamin A to as many as 250,000 child deaths every year.

    One excellent source of vitamin A is found in newly developed sweet potatoes with orange flesh. Orange sweet potatoes contain high levels of beta-carotene, which the body changes into vitamin A. Experts say orange sweet potatoes could help the Africans who are lacking in vitamin A. But, first, more people will need to be persuaded to eat them. Sweet potatoes need a better image in Africa. Jan Low with the International Potato Center says, “We do have an image problem with sweet potatoes. In many African countries, they are seen as a crop of the poor.”

    Ms. Low explains that sweet potatoes are mainly grown by poor women to feed their families in case another crop fails. The sweet potatoes commonly grown in Africa have white or yellow flesh. But they are low in vitamin A.

    Jan Low took part in a project to study how to market orange sweet potatoes to Africans best. She worked on an information campaign(活动) in Mozambique and Uganda. The campaign included radio messages about the nutritional(营养的) benefits of the orange sweet potato. They advertised its ability to “fight diseases, make you strong, clear you skin and make you look healthy”. In areas without radio, the campaigners spread the message through theater. The performances included singing, dancing and storytelling. And everywhere they went, the campaigners wore orange T-shirts and hats. They even drove orange cars.

    Dan Gustafson heads the Washington office of the United Nations Food and Agriculture Organization. He mentions the efforts in the past to increase the popularity of other nutritious crops. He says most of these efforts failed because organizers of the campaigns did not consider what people wanted to eat. People want to eat what they are familiar with. But Mr. Gustafson sees a better chance for the efforts to increase the popularity of the orange sweet potato in Africa. Except for the color, the orange sweet potato is almost the same as what people already eat. Dan Gustafson says, “I think this time the campaigners will succeed, because they have made enough advertisements and the difference between the vegetable they have advertised and what people already eat is not a radical one.”

    If you were like most kids, your mother told you there were three no-no's when it came to your fingers: Don't put them in an electrical outlet, don't stick them up your nose ( at least not in public ), and don't use them when you are counting.{#blank#}1{#/blank#}But experts in education and cognition now believe that using your fingers to do math is not only a perfectly good idea but may even help children become superior students.

    It certainly makes sense. When children count on their fingers, they take an abstract concept— mathematics—and translate it into the most basic and visual form.{#blank#}2{#/blank#} Even when we aren't actually counting on them, they still can help us on math problem,

    {#blank#}3{#/blank#}It activates when we respond to heat, pressure, pain, or the use of a given finger. Studying brain scans, researchers discovered that when students aged 8 to 13 work on subtraction (减法) equations, this region “lights up” on the scans, even if the students aren't using their fingers. The more complex the problem, the more activities are detected.

    The connection between finger use and math ability has been shown on old-fashioned math tests as well. With their eyes closed, first graders were asked to identify which of their fingers a researcher was touching,{#blank#}4{#/blank#}When college students were given the same quiz, the highest scores once again performed best on calculation tests.

    So what does all this mean? For one thing, parents and teachers shouldn't discourage children from counting on their fingers.{#blank#}5{#/blank#}Memorizing the multiplication tables may help, but it is not the best option. “I would like to see interesting and creative representations of ideas.” says Jo Boaler, a professor of math education.

    Recently, a series of activities have been designed to strengthen students' perception of their fingers. Maybe in the near future, there will be only two no-no ¹s regarding the use of fingers.

A. The first two laws of fingers are as true as ever.

B. There is a section of the brain, called the somatosensory finger area.

C. Researchers also stress that students simply learn better using visual tools.

D. Researchers are unimpressed by those students who finish quickly as well.

E. In fact, experts believe the brain is able to “see” a representation of our fingers.

F. That may sound simplistic, but the researchers offer an interesting explanation.

G. Researchers found those scoring highest on the finger-ID questions scored higher on a math test.

    Feeling sad is an important part of human nature.

    Jerome Wakefield, a professor at New York University, mentions that feeling down after your heart is broken is normal and may even be beneficial. Recently, Wakefield's students have been coming up to him because their parents are pressuring them to get help for their sadness; often the kids want no part of it. Rather than “listen to medicine,” they want to listen to their hearts. He believes these students' reaction represents an important part of human nature.

    Professor Diener, who has studied happiness for a quarter century, finds that the Scots and many other peoples like being sad, and don't appreciate being told they should be happier. “They say too much happiness might not be such a good thing, no matter where it comes from,” says Diener. He believes it's wrong for the “happiness industry” to send the message that not only can we all be happier, but we have a duty to be so. He argues that what is considered normal sadness is something we shouldn't avoid.

    Eric Wilson, a professor at Wake Forest University, made every effort to smooth out his habitual frown and wear a sunny smile, since a happy expression can lead to happy feelings. He even tried to be enthusiastic. When neither of these made him happy, he concluded that such a happiness movement was no good for him at all. Americans, love for happiness, he writes, creates an environment where sadness is not valued.

    These researchers believe the problem of continuous, extreme happiness should not be surprising, since negative emotions developed for a reason. Fear warns us against the presence of danger, for instance. Sadness, too, seems to be part of our DNA: monkeys, dogs and elephants all display something that looks like sadness. Being “up” all the time can cause you to play down very real threats.

    They believe that only by experiencing sadness can we experience the fullness of the human condition. Their studies show that when you are in a negative frame of mind, you become more logical and more creative. Abraham Lincoln was not limited by his dark moods, and Beethoven composed his later works in a sad state. Vincent van Gogh, Emily Dickinson and other artistic giants saw the world through a glass darkly.

    People who are somewhat unhappy are more motivated to improve both their own lot and the lot of their community. In contrast, people at the top of the happiness charts feel no such urgency. “If you're totally satisfied with your life,” says Diener, “you don't feel like working for change. Be careful when people tell you that you should be happier.”

Jealous Ken

    Dick and Ken lived in the same street. Both children had a good home and lots of nice things. {#blank#}1{#/blank#} In other words, Ken was a jealous(嫉妒的) boy.

    Dick and Ken grew up and got jobs. At first, they both cycled to work every morning. Then Dick bought a motorcycle. Every morning, Dick on his motorcycle rode past Ken on his bicycle, and Ken felt jealous. {#blank#}2{#/blank#} He was happy until Dick bought a car.

    Ken worked hard until he had enough money for a car. He bought a car, and it was as good as Dick's car. There were a lot of other cars on the road, so the journey to work was slower, but Ken was happy.

    {#blank#}3{#/blank#} So Ken worked very hard, and yesterday he bought an expensive new car. This morning Ken left home in his new car. {#blank#}4{#/blank#} But Ken was happy because his car was bigger, better and faster than Dick's car.

    Then he saw Dick behind him, but Dick was not in a car. Dick was riding a bicycle. It was a new bicycle. The cars moved very slowly, so Dick cycled past them easily. {#blank#}5{#/blank#} He watched from his big, expensive car and felt jealous.

A.     Dick was very proud of his new car.

B.     But after a year, Dick bought a bigger car.

C.     Both Ken and Dick walked to work every day.

D.    So Ken bought a motorcycle and he was happy.

E.     Ken watched as Dick cycled away in front of him.

F.     But Ken was unhappy because some of Dick's things were better than his.

G.    There were cars in front as far as he could see, and none of them could move.

    Imagine this: You're at the movies seeing the latest box-office hit. The leading actor chases down the film's bad guy before winning over the beautiful leading lady. What does he do next? He sucks on a cigarette.

    What's wrong with this picture? Doesn't the beautiful woman see her hero's yellow teeth? Doesn't she smell his smoky breath? And wouldn't the good guy have trouble chasing, since smoking causes a person to cough?

    But you don't see any of that when someone smokes cigarettes in the movies. And there is a lot of smoking in movies. Actors light up in more than 50 percent of youth-rated (G, PG, PG-13) movies, according to the American Legacy Foundation, which aims to put an end to smoking among young people. That means that Hollywood is showing 14 billion images of smoking to young people every year.

    All that exposure to on-screen smoking can influence teens to smoke. The Center for Disease Control and Prevention (CDC) argues that 44 percent of teens who begin smoking do so because they've seen smoking in movies. The CDC reports that teens are two to three times more likely to start smoking after seeing repeated smoking scenes in movies than teens who are lightly exposed to smoking in movies.

    Several organizations are working to remove smoking in youth-rated movies. And adults are not the only ones who care about this issue. Many teens are actively involved. Livia Clandorf, 16, of Chatham, New York, is a member of Reality Check, an organization that educates teens about what it considers to be the manipulative(巧妙处理的) practices of tobacco companies. Livia participated in an event called a "movie stomp(跺脚)". Reality Check rents out a movie theater and screens a youth-rated film that shows smoking, they stomp their feet and show disapproval by shouting “boo”.

    Record fires sweeping across the Amazon this month have been catching global headlines as scientists and environmental groups are worried that they will worsen climate change and threaten biodiversity(生物多样性).

    As the largest rainforest in the world, the Amazon is often called "the lungs of the world". It is also home to about 3 million species of plants and animals, and 1 million local people. The vast lands of rainforest play an important role in the world's ecosystem because they take in heat instead of it being reflected back into the atmosphere. They also store carbon dioxide (二氧化碳)and produce oxygen, making sure that less carbon is given off, mitigating the effects of climate change.

    "Any forest destroyed is a threat to biodiversity and the people who use that biodiversity," Thomas Lovejoy, an ecologist at George Mason University told National Geographic. "The shocking threat is that a lot of carbon goes into the atmosphere," he stressed. "Facing the global climate change, we cannot afford more damage to a major source of oxygen and biodiversity. The Amazon must be protected," U.N. Secretary General Antonio Guterres said.

    Data from the National Institute for Space Research (INPE) show that the number of forest fires in Brazil quickly increased by 82 percent from January to August this year from a year ago. A total of 71,497 forest fires were recorded in the country in the first eight months of 2019, up from 39,194 in the same period in 2018, INPE said. "It's reported that the forest areas in the Brazilian Amazon have decreased something between 20 and 30 percent compared to the last 12 months," Carlos Nobre, a researcher at the University of Sao Paulo, told German broadcaster Deutsche Welle.

    Brazil owns about 60 percent of the Amazon rainforest, whose drop could have severe results for global climate and rainfall. The size of the area ruined by fires has yet to be determined, but the emergency has transcended(超出）Brazil's borders, reaching Peruvian, Paraguayan and Bolivian areas.