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    Five hundred years ago, potatoes grew in South America. They were an important food for the people who lived in these high mountains. In other parts of the world, however, people didn't know about potatoes.

    The Spanish came to South America in the 1500s. They learned of potatoes and took some back to Spain. By 1570, people grew white potatoes in parts of Spain. By 1580, people in Italy were also growing potatoes.

    From Spain, potatoes travelled to France. In France, however, people were afraid to eat this new vegetable. They thought it was bad for health. Then the King of France tried to make his people eat potatoes. But for many years, the French still refused to eat potatoes.

    Potatoes reached England in a different way. In 1586, the English explorer(探险家) Drake stopped in Colombia. There he probably picked up some potatoes and took them back to England. At first, the English refused to eat potatoes, too. They used potatoes to feed their pigs and chickens.

    From England, the potato travelled to Ireland. The potato grew well in the poor soil of Ireland and soon it was an important food for the people in Ireland.

    In the early 1700s, Irish people brought potatoes to North America. By 1750, many people in New England were growing and eating potatoes.

    Can dolphins talk? Maybe they can't talk with words, but they talk with sounds. They show their feelings with sounds.

    Dolphins travel in a group. We call a group of fish“a school(一群)。” They don't study, but they travel together. Dolphins are mammals(哺乳动物)，not fish, but they swim together like fish in a school.

    Dolphins talk to the other dolphins in the school. They give information. They tell when they are happy or sad or afraid. They say” welcome” when a dolphin comes back to the school. They talk when they play.

    They make a few sounds above water. They make many more sounds under water. People cannot hear these sounds because they are very, very high. Scientists make tapes of the sounds and study them.

    Sometimes people catch a dolphin for a large aquarium(水族馆). People can watch the dolphins in a show. Dolphins don't like to be away from their school in an aquarium. They are sad and lonely.

    There are many stories about dolphins. They help people. Sometimes they save somebody's life. Dolphins' meat is good, but people don't like to kill them. They say that dolphins bring good luck. Many people believe this.

    Most people agree that trees look nice, but not everyone knows that trees can also help cities save money. A few years ago, the US Forest Service studied trees in Chicago. They found that just one tree can save a city hundreds of dollars over its lifetime.

    Trees can save money by helping people save energy(能源). Trees stop the sun shining on buildings. They also block(挡住) the winter wind. That helps people use less energy to make their homes or offices warm or cool. Saving energy is saving money.

    Trees have another way to help a city save money. When it rains, there will be a lot of water in a city's sewers (下水道). Cities need lots of money to clean that water. But before the rainwater gets to the dirty sewers, trees can take some into themselves. With the help of trees, there is less water to clean.