Technological change is everywhere and affects every aspect of life, mostly for the better. However, social changes are brought about by new technology are often mistaken for a change in attitudes.

    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.

Letter One

Dear Editor,

    After I finish my homework, I often go online and chat with my friends. Sometimes I play Internet games. But my parents hate to see me playing games on the computer. Maybe they have heard too much news about how QQ and Internet games harm children. Once I went to a net bar to play games after school. But after that I told my parents that I was playing basketball at school. I said so because I didn't want to make them unhappy. I feel bad about it. However, I need to rest for a while by playing computer games after studying for a long time. I really want my parents to understand that. Do foreign parents do the same to their children? Please help me.

Li Ping, Nantong

Letter Two

Dear Li Ping,

    I think it's not strange for parents to keep their children away from anything bad. Foreign parents will do the same as your parents! They may not let their children watch TV for too long a time, or like your parents, they don't want their children to play computer games.

    Talk to your parents and be honest to them, I think. Tell them what you are doing and why you are doing so to make them understand you. It's never good to do things behind your parents' backs. They aren't fools as you think sometimes! Our parents seem to know what is the best for us. Remember: to be honest is the best way.

Good luck,

Rebecca

    China now has 52 sites included on the UNESCO World Heritage List, which was established to safeguard unique and irreplaceable cultural and natural sites around the world. Let's have a look at some of them, which may give you some clues on your next travel plan.

    Mausoleum of the First Qin Emperor

    The Mausoleum of the First Qin Emperor is located in Lintong county, near Xi'an city, capital of Shaanxi province. A total of 8,000 life-size terracotta warriors, chariots and horses, and hundreds of bronze weapons have been unearthed from it. Many state leaders and experts worldwide believe that the discovery of the mausoleum is a major archeological find and can be called the eighth wonder of the world, paralleling Egypt's pyramids.

    Kulangsu, a Historic International Settlement

    Gulangyu Island, known in the local dialect as Kulangsu, is located on the entry of the Jiulong River, facing the city of Xiamen. The island was occupied by at least a dozen countries, including Great Britain, France and Japan. As a result, Western culture grew rapidly there in the 19th century, especially music. With such a harmonious blend of Western music and Eastern culture, Gulangyu is naturally referred to as the "island of music". It is famous for its outstanding musicians and musical instruments.

    Qinghai Hoh Xil

    Hoh Xil, which means "beautiful girl" in Mongolian, is located in the north-eastern end of the Qinghai-Tibetan Plateau. Hoh Xil National Nature Reserve is China's largest and the world's third largest uninhabited area. Because of the high altitude and fierce weather, it is impossible for people to live there, and therefore, it is a paradise for wildlife and home to more than 230 species of wild animals including endangered species such as the Tibetan antelope, which is recognized as the National Class I Protected animal.

    Huangshan Mountain

    Huangshan, known as "the loveliest mountain of China", lies in the south of Anhui province in eastern China. The scenic area covers 154 sq km, and is famous for its peaks, rocks, pines, clouds and springs. It also has a rich cultural heritage. Xu Xiake, a famous traveler of the Ming Dynasty (1368-1644), visited Huangshan twice, and described it in a poem, calling it the best of all mountains in China. Today it holds the same fascination for visitors, poets, painters and photographers.

    On April 2, we said goodbye to Tiangong I, China's first space lab. According to the China Manned Space Agency（中国载人航天）, Tiangong I re-entered the Earth's atmosphere （大气层）and fell into the South Pacific Ocean.

    There are many spacecraft that are still in orbit above the Earth. They are flying at heights ranging from 300 to 1,000 kilometers. After finishing their trips, they will all re-enter the Earth's atmosphere like Tiangong I.

    There are two types of re-entries：controlled（受控的）re-entry and uncontrolled re-entry.

    Some satellites（卫星）and manned spacecraft come back to the Earth in a controlled re-entry. Scientists calculate（计算）the path of the falling spacecraft and its speed. They can guide the spacecraft to fall in a chosen area. In 2017,Tianzhou I, China's first cargo（货运）spacecraft, was directed to fall in the South Pacific Ocean.

    Some spacecraft may have problems while in space, or are simply no longer usable after a certain amount of time.  These craft come back in an uncontrolled re-entry.  It is hard to tell when and where these spacecraft will fall until the last few hours. The US space station Skylab came back partially uncontrolled in 1979. Parts of the station fell in western Australia, but no one was injured.

    During re-entry, most of the spacecraft will burn up while passing through the Earth's atmosphere. Only a small amount of the debris（碎片）will reach the ground.

    The debris typically ends up falling into the ocean, China Daily reported. Tiangong I weighs about 8.5tons. The amount of debris that falls to the Earth might be about 1 to 1.5 tons, the Beijing News reported.  That is about the same weight as a car.

    Your next car could have two seats, three wheels—two in front and one in the back and a top speed of more than 100 miles per hour. Elio Motors plans to make such a tiny car named the Elio. Its two seats sit front and back instead of side by side. The driver is positioned in the center with the passenger directly behind.

    The starting price for the car is just $6,800. It has only one door, on the left side, which cuts a few hundred dollars off the manufacturing costs. Having three wheels also makes it cheaper. It has air conditioning, power windows and door locks and an AM/FM radio. More features can be ordered through Elio's long list of suppliers. Elio will also sell the cars directly through its own stores and not through franchised dealers (特约经销商).

    Paul Elio dreamed as a kid that he would one day own a car company called Elio Motors. In 2008, tired of high gas prices, he started working on a car that burns gas in a more effective way. Equally important to him was creating US manufacturing jobs and making the car inexpensive enough to attract buyers who might otherwise be stuck in their old, unreliable cars. "Whatever matters to you, this can move the needle on it, he said.

    Already, more than 27,000 people have reserved one. Paul hopes to make 250,000 cars a year by 2020. So far, reservation holders are those who will use the Elio as a second or third car for work. Paul Elio believes the car will interest college students as well as used-car drivers who want something newer and more reliable, though.