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    Many things can make summer great: swimming, camping, and the World Cup! The 20th FIFA World Cup will take place in Brazil from June 13 to July 14. Get ready for it!

    People around the world love football. The sport is very easy and cheap to play. All you need is a ball. Anyone or any country, rich or poor, can play it. A small or poor country like Ghana could never beat the US at the Olympics. But they can send the US home at the World Cup.

    In countries like Brazil and England, football is so popular that it has become part of their culture. People there will be very happy and proud if their national team wins the World Cup. This summer thousands of England fans will go to cheer for their team in Brazil, even though the trip could cost each of them 10, 000 pounds!

WorldCupNumbers

●TheFIFAWorldCuptakesplaceeveryfouryears.

●Thirty­twoteamsplayinthe World Cup.

●TheWorldCupusuallylasts 30 days.

●Onlyeight nationshavewonthe 19 WorldCuptitles(冠军头衔). Brazilisontopofthelistwith 5 wins. OthersincludeItaly, Germany, Argentina, Uruguay, England, FranceandSpain.

●AccordingtoFIFA, 3.2 billionpeoplewatchedthe 2010 WorldCup. Thatisnearlyhalfoftheworldpopulation.

(From 21st Century, April 28, 2014)

    Science is proving what pet owners have long believed: Dogs understand what we're feeling. Especially, dogs can recognize(识别) the difference between a happy and an angry human face, a study published Thursday in Current Biology suggests.

    It's the first research to show that dogs are sensitive (敏感) to our facial expressions, says the author Ludwig Huber at the University of Veterinary Medicine, Vienna.

    In the Austrian study, 20 different kinds of pet dogs were taught to play a computer game through a series of exercises. In the first step, the dogs were shown two touch screens, one with a circle and one with a square. Through the exercises, they learned that a treat would appear if they chose the right one.

    Eleven of the 20 dogs were able to catch on to rules of the game and make it to the next test, where they were shown photos of happy and angry faces. The dogs were rewarded if they picked certain expression correctly. During the test, the dogs were shown only the upper half or the lower half of a face.

    It was easier to teach the dogs to choose a happy expression than an angry one, suggesting the dogs do indeed understand the meaning behind the expression, Huber says.

    As a test, the dogs were then presented with: the same half of the faces they saw during the training, but from different people， the other half of the faces used in training， the other half of new faces， the left half of the faces used in training.

    In the cases, the dogs chose the right answer 70 to 100 percent of the time.

    Dogs who had been trained to recognize an expression of anger or happiness on the upper part of a face could find the same expression when shown only the lower part. Huber says, "The only possible explanation is that they recall from memory of everyday life how a whole human face looks when happy or angry."

    Dog owners know their pets not only recognize emotions but also understand the feelings.

    Teenagers are known for being creative and full of new ideas. Let's have a look at these teenage inventions that might change the world.

    Butterflies are common all over the world, but butterflies in hotter countries are usually bigger and more brightly colored than those in cooler countries, and they are more different kinds.

    Usually the male(雄性的)butterflies are more brightly colored than the females. The females have bigger and heavier bodies since they carry the eggs. The bright colors of the males help to attract the females, and the duller(较暗淡的)colors of the females make them less likely(可能的)to be caught by enemies before they have laid their eggs.

    Some butterflies hare bright pattern colors on the upper surface of their wings that show when flying, but when they rest on a tree or leaves, they close their wings. On the undersides of their wings there are green and brown marks which look like the tree or leaves. They are then difficult to be seen. The best example of this is the Dead Leaf Butterfly. When its wings are closed, it looks exactly like a dead leaf. There are even marks that look like the holes in a dead leaf. When the butterfly is run after by a bird, it closes its wings and seems to have disappeared completely.

    Many butterflies have round marks on their wings that look like eyes. The round marks have a useful function(功能). When the butterflies are resting, their wings are closed, and these marks can't be seen. When a bird sees one, and begins to attack it, the butterfly will open its wings. The bird thinks that it sees two eyes staring at it, frightened, and flies away.

    Humans have learnt many things from nature. These things have helped us in our daily life. The latest thing is self-repairing clothing.

    Scientists have developed a special way for clothing to repair rips and tears by itself, without the need for sewing. It works with materials such as cotton, linen and wool. The scientists are from the Naval Research Office and Pennsylvania State University in the USA. Scientists Dr Walter Dressick and Dr Melik Demirel looked at how a squid can cling on to things so well. The research team found a protein in the rings of teeth that cover the suckers on a squid. The protein is similar to the one found in the silk that spiders use to make spider webs. It is very strong and elastic.

    The new protein has been developed as part of a coating, which is put on clothes. When the coating is dipped in water, the area around the rip or tear joins together in less than a minute. This could help clothes last longer and save money for us. It could also be useful for military and survival clothes. People like soldiers and mountaineers would be safer if they had clothes that could be repaired quickly and easily. Professor Demirel spoke about the invention. He said," The coatings are thin, less than a micron, so they wouldn't be noticed in everyday wear." Then he added, "Even thin, they increase the overall strength of the material. For the first time, we are making self-healing textiles."

    The movie The Martian (《火星救援》) is very popular among space lovers. It shows an astronaut trying to live on Mars.

    Although the idea of living on Mars is great, the reality does not look so good. Mars does not have a friendly atmosphere (大气层) for humans. There is very little oxygen there. And because it is too far away from the sun, it is also very cold there. Sometimes the temperature on Mars can be -133℃. This is much too cold for humans.

    However, scientists say it might be possible to live there even without a good atmosphere. Daytime on Mars is almost the same as Earth's. It means there's enough sunlight to grow plants inside safe buildings. However, they would have to grow in soil from Earth. Mars does not have a strong enough atmosphere to stop the radiation (福射) coming from space, which makes it dangerous to grow things in the soil.

    The radiation also causes problems for our health. One way to live there is to build homes underground or in the rocks on the planet. This can help humans keep away from the radiation and keep warm.

    When could we live on Mars? Scientists are hoping to make it possible to live on Mars. Let's wait and see.