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.”

    Elizabeth Blackwell was born in England in 1821, and moved to New York City when she was ten years old. One day she decided that she wanted to become a doctor. That was nearly impossible for a woman in the middle of the nineteenth century. After writing many letters asking for admission(录取) to medical schools, she was finally accepted by a doctor in Philadelphia. She was so determined that she taught school and gave music lessons to get money for the cost of schooling.

    In 1849, after graduation from medical school. She decided to further her education in Paris. She wanted to be a surgeon(外科医师) , but a serious eye problem forced her to give up the idea.

    Upon returning to the United States, she found it difficult to start her own practice because she was a woman. By 1857 Elizabeth and her sister, also a doctor, along with another woman doctor, managed to open a new hospital, the first for women and children Besides being the first woman physician and founding her own hospital , she also set up the first medical school for women.

    Nisha Pradhan is worried. The recent college graduate just turns 21 and plans to live on her own. But she's afraid she won't be able to stay safe. That's because she isn't able to smell.

    Back home, her family do her smelling for her. She's moved in with them for now, but she's looking for a place of her own. “Now that I'm searching for ways or place to live as an independent person, I find that the sense of smell is important to how we live our lives,” Pradhan says.

    She says when she was a child she liked to eat and ate a lot. But there came a point where she lost interest in food.

    “One of the first things that people notice whenever they have a smell problem is that food doesn't taste right any more,” says Beverly Cowart, a researcher. That's because eating and smell go hand in hand. How food tastes often rely on what we smell. “When you lose your sense of smell, your whole sense of food flavors changed and reduced,” Cowart says, “You can still taste the basic tastes. What you're missing are the small distinctions.”

    “When I go out to eat I have often found that food is very tasteless to me. I never feel full,” she says. “I think a lot of us today like to pretend to be food lovers and we all like to talk about 'Oh, I think this could use a little bit more flavor,' or ‘I think this has a hint of meat,' I can't really participate in those conversations,” she says.

    Pradam thinks her smell loss also may have affected her memory. Pradhan may be on to something, according to biologist Paul Moore. “When smell signals come in, you feel about them first. And then you think about it and then the memory is laid down. So without the feel part, the thinking about its part doesn't come. And that means no new smell memory gets created.”

    On May 29, 1973, Thomas Bradley, a black man, was elected mayor of Los Angeles. Los Angeles is the third largest city in the United States, with a population of three million. About sixteen percent of the city's population are black.

    News of this election appeared on the front pages of newspapers everywhere in the United States. Here is how one major newspaper reported the event.

    LOS ANGELES ELECTS BRADLEY MAYOR UNSEATING YORTY

    BLACK WINS 56% OF VOTES

    Bradley called his victory over Yorty "the fulfillment of a dream". During his childhood and youth, people had kept telling him, "You can't do this, you can't go there, because you are a Negro." Nevertheless he had won a decisive victory over a man who had been won 43.7 percent.

    Los Angeles voters have had many opportunities to judge. Thomas Bradley had to form an opinion of him. The son of a poor farmer Texas, he joined the Los Angeles police force in 1940. During his twenty-one years on the police force he earned a law degree by attending school at night. He was elected to the city council years ago.

    At the time of the Los Angeles election, three other American cities already had black mayors, but none of these cities had as large a population as Los Angeles. Besides, the percentage of blacks in those other cities was much larger. Cleveland, Ohio, had thirty-six percent black when Carl Stokes was elected mayor of Cleveland in 1967. In the same year Richard Hatcher was elected mayor of Cary. In Newark, New Jersey, sixty percent of the population were black when Kenneth Gibson was elected in 1970. Thus election of a black mayor in those cities was not very surprising.

    In Los Angeles, thousands of white citizens voted for Thomas Bradley because they believed he would be a better mayor than the white candidate. Bradley had spent forty-eight of his fifty-five years in Los Angeles. Four years ago, Bradley lost mayoral election to Yorty. This time Bradley won.

Isatou Ceesay was born in 1972 in a small village in Gambia, Africa. As a teenager, Ceesay was forced to drop out of school because of poverty. She carried some goods with many girls like her to sell in the market to raise herself At that time, the plastic bags, being strong and light, became popular in Gambia. The problem was that people did not reuse the bags and simply threw them behind their homes. Over time, the houses were surrounded by trash.

Ceesay lived in such an environment for many years. She kept learning from the surrounding environment and planned to take action to change. In 1997, she started a recycling movement called One Plastic Bag in Gambia. She educated women in Gambia to recycle plastic waste into income for themselves. In the beginning, the movement had a mission to educate their village colleagues about the need to reuse garbage and recycle plastic waste, rather than letting the garbage increase behind their homes.

Over time, the movement became big and able to support and provide income for women around. It was also able to greatly reduce plastic waste in Gambia. But the work of collecting trash turned to be taxing. During the rainy season, plastic waste became wet and difficult to take, and after that it still took patience to dry it before it could be processed.

Ceesay said, "As a habit, people are used to pouring their garbage behind their houses, and because it is not visible, they forget it. But the bad effects again knock on your door very quickly — dirty air, various diseases and so on. Of course, if one man's house is clean but his neighbor's is not, then the man is also not healthy."

For 17 years, Ceesay has contributed to one of the most important problems about the plastic waste. In 2012, she got the TIAW Difference Maker Award in Washington, DC, United States. Her story was written into a book, which inspires many others to join or become makers of change in their own communities.

Having a study partner has many advantages. Of course, you can always study alone at home. But you'll miss the benefits that come from learning with a friend or two. Why should you think of finding a study partner or a study group? {#blank#}1{#/blank#}

It can reduce distractibility(注意力分散).

Staying focused is one of the biggest challenges students have to overcome. When you have a study partner, it will be easier to achieve. With common goals in mind, you will focus on the result. 

You understand the material faster than alone.

{#blank#}2{#/blank#}Let's face it: two brains are always better than one. Besides, you can learn some new study methods from your study partner. 

{#blank#}3{#/blank#} 

Besides staying focused and learning faster, you can benefit from testing each other. Quizzing(测验) before the exam can help both of you to find out the areas that need more attention. 

Studying with someone motivates(激励)every member.

Studying with a partner can motivate both parties.{#blank#}4{#/blank#}Having a friend to depend on in these difficulties can be helpful not only from an educational standpoint but also from a psychological(心理的) one. 

Learning becomes organized yet fun.

Last but not least, it can be enjoyable to share your study journey with another person. Long evenings in the library will seem less lonely if you're with a friend. {#blank#}5{#/blank#}It will turn the learning into a fun yet organized process. 

A. Here are several reasons. 

B. Also, it is nice to rest and drink coffee once in a while together 

C. Study partners can test each other. 

D. Having a study partner can help you learn faster. 

E. Learning can get stressful and cost too much energy.