What is the first thing you want to do when you see someone yawn(打哈欠)? You want to yawn, too! Yawning is contagious.

    Scientists have found that all people yawn. Babies start to yawn even before they are born. The earliest yawn takes place when a baby is still inside its mother. When young children are about one year old, they start to yawn when they see others yawning. That's why scientists seem to think yawning is contagious.

    It's no secret that yawning is contagious, but why do we yawn? Well, scientists are not really sure.

    Some think we yawn because we feel bored. Recently scientists studied two groups of students between the ages of 17 and 19. One group watched music videos, and the other watched a boring color test. Scientists compared the numbers of their yawns and found that the color test group yawned more times than the video group.

    Another reason about yawning has to do with breathing. Some scientists believe that when we are bored or tired, we breathe more slowly. As our breathing slows down, we cannot get rid of(去除) enough carbon dioxide (CO₂) in our bodies. When there is too much carbon dioxide, our bodies will tell the brains (大脑) to breathe deeply. The result is a big yawn.                                                           

    In 2007, scientists suggested a new reason. They said that the reason people yawned was to cool down their brains. These scientists found that people who were warmer than others yawned more often.

    Scientists are still trying to find out why yawning happens and why it is so contagious. But they are only sure that when one person yawns, almost everyone else nearby wants to yawn, too.

    Why do we like drinking water from plastic bottles? Some people think it is healthy and clean. Others drink bottled water because it's easy--you can carry it around with you. In hot countries, like Greece, we often buy bottles of cold water in the summer.

    However, making tots of plastic is not a good idea for many reasons. First of all, we need a lot of oil for plastic products. We usually use oil as a source(资源) of energy. If we reduced the number of bottles we made, we wouldn't need so much oil. Plastic bottles also pollute the environment. If we recycled all our plastic bottles, we wouldn't need so much space for rubbish dumps. But in Greece, we don't recycle much of the plastic we use. In 2006, Greeks recycled only about 10% of plastic waste. The rest became rubbish on land and in rivers and seas.

    So next time you want to throw away a plastic bottle in the litter bin, stop and think. If you recycled it, you would help the environment. But what can you do when there isn't a recycling bin near you? Well, there are lots of useful ways that you can use your bottles again. For example, an empty bottle makes a great piggy bank for your pocket money, and if you cut a bottle in half, you will have a plant pot. Go green! You can make a difference.

    Imagine one day, the water taps (水龙头) in your house stop running. You have to buy water from shops. And still there isn't enough for everyone. Your mother has to save the family's shower water to do other things. Would you be able to stand that kind of life?

    Probably not. But that's what kids in Yemen are experiencing. Experts said Yemen is going to be the first country in the world to run out of water. According to a report, the capital, Sana, will run out of drinking water as early as 2025.

    Because of the shortage, the government often cuts the water supply(供应). Hannan, an 18-year-old from Lahej, told Times, "In a good week we'll have a water supply all week. But then the following week there will be water only for a day or two."

    Hannan said only rich people have enough water to use. They can buy water from the shops or from the water trucks. Private companies own the trucks. They travel around the city every day to sell water—at very high prices. "A lot of people can't afford it," she said.

    The average(平均) person in Yemen uses 100 to 200 cubic(立方) meters of water per year. That is far below the international water poverty(贫困) line of 1,000 cubic meters.

    The government is thinking of making use of seawater. But it will cost a lot and it may not happen soon enough to help the people of Yemen.

    The coffee shop Starbucks will give people a discount if they bring their own cups. It wants to cut down on the number of paper cups that are put in the rubbish bins. It is part of a two month experiment in cafes in England. Starbucks wants to reduce waste and recycle more, The president of Starbucks in the UK said, "We are very happy to increase recycling rates(比率)，and reusable cups are a key part of our waste reduction plan." Bosses will decide later if they will continue the discounts. People who bring their own cups will not get a discount on the cafe's cheaper filter coffee.

    The problem of paper cups has been in the news a lot. Around seven million cups are thrown away every day. Reporters say that some cafes lie about how many paper cups they recycle. The reporters say the cafes do not recycle as many cups as they say. Customers wrongly believe that a coffee shop is environmentally friendly. Less than one in 400 paper cups at coffee shops are recycled. A coffee drinker said she would bring her own cup. She said, "I am so sad that cafes recycle so little. I thought they were more responsible."