Dolphins (海豚) live in a dark underwater world. It's often impossible to see each other or anything else around them, so sound plays an important role in their survival. To communicate with each other, dolphins produce all kinds of sounds.

    Only other dolphins understand what the sounds mean. Scientists haven't uncovered their secret communication, except for one kind of whistle. It might last less than a second, but this whistle is a big deal. Why? Because these whistles are actually names of dolphins — and every dolphin has one. Scientists call these sounds a “signature whistle.” When other dolphins hear the whistle, they know which dolphin is calling.

    Dolphins often hunt by themselves but still need to stay connected to the group. Since they can't always see each other, dolphins use their signature whistles to check in with other dolphins hundreds of yards away. “In coastal areas, dolphins exchange whistles even when they're a third of a mile apart,” says Greg Campbell, who studies animals. That means dolphins shout out to group members that might be nearly five football fields away.

    What's amazing is who names the baby dolphin. Not the mother. Not an auntie dolphin or another group member. Scientists believe the baby dolphin itself comes up with the signature whistle. Like human babies, a baby dolphin plays with sounds throughout its first year. While testing its sound skills, a baby dolphin is doing something amazing. It's creating or figuring out its signature whistle. How or why it chooses its signature whistle is not clear. Studies show that most of the time the signature whistle is nothing like its mother's or group members' whistles.

    When the baby dolphin is about a year old, its signature whistle is set. It repeats it often so the other dolphins learn to recognize it.

    Deciphering(破译) dolphin names is just the beginning of figuring out what dolphins communicate about. Do they chat about sharks? Discuss the tides? Maybe they even have a name for people. Someday scientists are to decipher the rest of dolphins' communication.

    Children's lives have changed greatly over the last 50 years. But do they have a happier childhood than you or I did?

    It's difficult to look back on one's own childhood without some element of nostalgia (怀旧的). I have four brothers and sisters, and my memories are all about being with them. Playing board games on the living room floor, or spending days in the street with the other neighborhood children, racing up and down on our bikes, or exploring the nearby woods. My parents scarcely appear in these memories, except as providers either of meals or of severe blame after some particularly risky adventure.

    These days, in the UK at least, the nature of childhood has changed dramatically. Firstly, families are smaller, and there are far more only children. It is common for both parents to work outside the home and there is the feeling that there just isn't time to bring up a large family, or that no one could possibly afford to have more than one child. As a result, today's boys and girls spend much of their time alone. Another major change is that youngsters today tend to spend a huge amount of their free time at home, inside. More than anything this is due to the fact that parents worry far more than they used to about real or imagined dangers, so they wouldn't dream of letting their children play outside by themselves.

    Finally, the kind of toys children have and the way they play is totally different. Computer and video games have replaced the board games and more interesting activities of my childhood. The irony (令人啼笑皆非的事情) is that so many ways of playing games are called “interactive”. The fact that you can play electronic games on your own further increases the sense of loneliness felt by many young people today.

    Do these changes mean that children today have a less relaxing childhood than I had? I personally believe that they do, but perhaps every generation feels exactly the same.

    Sports are the base of my life, next to my mother who raised me when my dad left us. I have been into sports since I was six years old. I have known many coaches and heard hundreds of their tips, but they usually focused on drills to develop my skills and reach the next level of play.

    When I was in Senior Two, I met the new school basketball coach, Brian Pawloski. I thought I was certain to be selected for the school team since I had been in it the year before. I showed up to the tryouts and put out about 90% effort since I thought I'd make it with no problem. That was a big mistake.

    Brian Pawloski is the hardest-working coach I have ever met. He didn't expect 100% effort, he expected 200% effort. One example: he once made us do 40 suicide drills for the 40 lay-ups (投篮) we missed in a game. Some think this is crazy, but it isn't. After this conditioning practice, as we were getting a cup of cold water to drink, I said, "coach, that was the best practice I ever had." I was completely sincere. This man was and is the person who influenced me most at my high school. He expects us to be excellent not just on the court but in the classroom. If I am not working on basketball, I am reading a book that he thinks will help us better understand life's challenges, including Wooden, Coach, and The Screwtape Letters.

    In the first two years I slacked off, not putting forth my full potential. Now, unlike the coaches of my youth, this man was interested in how he did off the court. He always made sure I kept up with my studies and was able to be trusted. I can honestly say that on other coach has given me so much advice on how to succeed in basketball, but more importantly, in life. My school is lucky to have such a great person to teach, coach and influence their students. I will always remember my high-school basketball days as one of the hardest times I have ever worked in my life not only in basketball but in my growth as an individual.

    A build-it-yourself solar still（蒸馏器） is one of the best ways to obtain drinking water in areas where the liquid is not readily available. Developed by two doctors in the U. S. Department of Agriculture, it's an excellent water collector. Unfortunately, you must carry the necessary equipment with you, since it's all but impossible to find natural substitutes. The only components required, though, are a 5＇  5＇ sheet of clear or slightly milky plastic, six feet of plastic tube, and a container — perhaps just a drinking cup — to catch the water. These pieces can be folded into a neat little pack and fastened on your belt.

    To construct a working still, use a sharp stick or rock to dig a hole four feet across and three feet deep. Try to make the hole in a damp area to increase the water catcher's productivity. Place your cup in the deepest part of the hole. Then lay the tube in place so that one end rests all the way in the cup and the rest of the line runs up — and out — the side of the hole.

    Next, cover the hole with the plastic sheet, securing the edges of the plastic with dirt and weighting the sheet's center down with a rock. The plastic should now form a cone(圆锥体) with 45-degree-angled sides. The low point of the sheet must be centered directly over, and no more than three inches above, the cup.

    The solar still works by creating a greenhouse under the plastic. Ground water evaporates (蒸发) and collects on the sheet until small drops of water form, run down the material and fall off into the cup. When the container is full, you can suck the refreshment out through the tube, and won't have to break down the still every time you need a drink.

    Of all the things we eat and drink, water is the most important. Not all people realize this, but it is quite true. The human body can live without food for a long time, but two or three days without water usually result in death.

    Many people do not understand how much water the human body needs, but many people do not drink enough, especially in the hot weather. Most people drink when they are thirsty but often need more water after exercises.

    65 to 70 percent of the human body is water. Water is important in several different ways. Most people need five to seven litres of water every day, but we need not drink this amount because a lot comes from the food we have. If we don't have enough water, however, we will feel tired and many become ill. Do you know what the best drink is? Yes, you are right. Cold water!

Welcome to your future life!

    You get up in the morning and look into the mirror. Your face is firm and young­looking. In 2035, medical technology is better than ever. Many people at your age could live to 150, so at 40, you're not old at all. And your parents just had an anti­aging (抗衰老的) treatment. Now, all three of you look the same age!

    You say to your shirt, "Turn red." It changes from blue to red. In 2035, "smart clothes" contain particles (粒子) much smaller than the cells in your body. The particles can be programmed to change your clothes' color or pattern.

    You walk into the kitchen. You pick up the milk, but a voice says, "You shouldn't drink that!" Your fridge has read the chip (芯片) that contains information about the milk, and it knows the milk is old. In 2035, every article of food in the grocery store has such a chip.

    It's time to go to work. In 2035, cars drive themselves. Just tell your "smart car" where to go. On the way, you can call a friend using your jacket sleeve (袖子). Such "smart technology" is all around you.

    So will all these things come true? "For new technology to succeed," says scientist Andrew Zolli, "It has to be so much better that it replaces what we have already." The Internet is one example-what will be the next?