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.

    With the development of science and technology, our daily life is becoming more colorful and more convenient .

    According to a new study, cats may be just as smart as dogs. Both cats and dogs may have episodic memory（情景记忆）, similar to that of human beings.

    The discovery shows that cats can recall memories of positive experiences like eating a delicious snack. The study was a test of episodic memory. Episodic memory means memory of past experiences that happened at a special time and place.

    In the test, cats were led to four open bowls of food. They were allowed to eat from two of them. After fifteen minutes, empty bowls took the place of the old ones. Then the same cats returned to look for food again. They spent more time searching for the old bowls.

    It seemed that the cats were able to remember the information of “what” and “where” about the bowls. This discovery suggests that they may have episodic memory. However, it's still not clear whether cats can truly experience past memories in the same way as human beings do. “It's difficult to know whether the cats can subjectively（主观地）remember the experience,” Nick Diamond, a researcher at the University of Toronto, explained.

    Still, the test plays an important role in the development of memory research in animals. “It opens the door to new studies. How long can cats' memories last? We may do some research on this in the future,” Professor Laurie Santos from Yale University told BBC News.

    The road to new discoveries is long and difficult. Though there are lots of problems to be solved and discussed along the way, such studies do lead us a step closer to the final success.

    Have you ever stayed in a hotel? Most Chinese hotels often provide guests with things like disposable (一次性的) toothbrushes, toothpaste, shampoo and slippers. Many guests like the idea because they don't have to bring their own. But, if you travel to Beijing, remember to bring your own things. Starting from June, some hotels in Beijing will no longer provide guests with these disposables. They want to ask people to use less disposable things.

    Many disposable things are made of plastic. People throw them away after only using them once. It is a waste of natural resources (资源) and is very bad for the environment. Do you know, one Chinese person makes as much as 400kg of waste a year! Most of that waste comes from disposable things. In Beijing, people throw away about 19,000 tons of plastic bags and 1,320 tons of plastic lunch bowls every year! Plastic can take between 100 and 400 years to break down. So the less plastic we throw out, the better. So, wherever you travel, bring your own things and use them again and again.

    Back at home and school, you can also do something to make our world a better place. Try to do these things in your daily life: Use cloth shopping bags, not plastic ones. After using a plastic bag, wash it out and let it dry. Then you can use it over and over again. Do not use paper cups. At your school canteen(食堂), use your own bowl and chopsticks instead of disposable ones.