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We've all heard of mermaids. They are the beautiful half-human, half-fish creatures(生物). They have the head and body of a human and the tail of a fish. We also know that mermaids only exist in fairy tales. But where did all the stories about these creatures come from? If you have ever seen a manatee, then you might have an idea.
Manatees, which are also called sea cows, are mammals(哺乳动物) that live in the sea. Since they are mammals, they have to swim up to the surface to breathe air. Many people believe that the story of the mermaid began with the ancient sailors who saw the manatees putting their heads out of the water to breathe. Because manatees are upright when they do this, it looks like they are standing. If a sailor saw a manatee doing this from far away across the sea, it is possible that the sailor would mistake the manatee for a creature that is half-human, half-fish.
Mermaids are described as having very long hair. This is probably because manatees like to swim up to the surface of the water in areas where there is sea grass. Manatees eat all kinds of plants in the sea, including sea grass. The sea grass around the manatee's head when they eat could create a picture of long hair.

Manatees also have powerful tails that are very similar to the fish-like tail of a mermaid. The sailors probably watched manatees come up for air and then swim back below the surface, using their paddle-shaped tails. This would explain why the sailors thought mermaids had fish-like tails.

    All over the world the need for more laptops and computers increases each year. Networks have been part of our life. Probably everyone with a portable device （移动设备）has once logged on to a public WiFi network without paying for it, while they are having a coffee, on a train, in a shopping mall or at a hotel. However, is this kind of public WiFi network safe?

    Some networks are better protected than others because encryption （加密）methods are used. Therefore, they are safer than others. But a survey in 2015 showed that more than 950 million records were not protected, including addresses, emails, birth dates, phone numbers, passwords and so on. These open WiFi networks are really not safe, because it is very easy for hackers （黑客） to break into the operating system and get people's private information.

    Most smartphones and laptops, by themselves, search and connect to WiFi networks. They usually prefer a network with a connection that has been used before. Hackers' devices are able to record these searches and look like the trusted WiFi networks. When these smartphones and laptops log on to the networks which are not real, hackers can easily steal their private information.

    So next time, when we want to use our laptops or our smartphones in public places which offer free WiFi networks, please think it twice or take safe measures before using them.

    If music makes you smarter and exercise helps you to think, surely exercising to music can turn you into an intelligent(聪明的) person.

    A team of scientists from Ohio State University did tests on 33 volunteers who were getting better from heart problems following operation(手术). They found that people who exercised while listening to "The Four Seasons" did much better on language ability tests than without music.

    "Facts suggest that exercise improve the learning ability of people with heart problems," said the scientist Charles Emery, who led the study. "And listening to music is thought to enhance understanding. We just wanted to put the two results together." he added.

    The volunteers said they felt better after exercising with or without the music. But their improvement on the test doubled after listening to music during exercise. Scientists have shown it is true that music can be good for health. It helps cut down stress, sadness and nervousness. And it also wakes up the body and improves memory and thoughts.

    In medical fields, music is used widely for patients who have had headaches before and after operation. "The Four Seasons" was used because of its soft tempo(节拍) and better results in earlier research.

    "Exercise seems to cause better changes in the nervous system and these changes may have a direct result on learning ability." Emery said. Scientists have been studying the result of music on understanding since the early 1950s. By 1990, scientists were using Mozart's music to help children with speech disorders. Mozart was chosen because his music is not overexciting. A study showed students who listened to Mozart scored higher marks in an intelligence test. With important exams coming, your parents will not probably allow you to listen to music. But perhaps now you have good reasons to argue with them.

    We all know that many women like to wear dresses. They enjoy many kinds of colourful and popular dresses. But have you ever heard of a 4D dress?

    Jessica Rosenkrantz in the USA used 3D printing technology to make a very special and new dress. It will help with the problems of different styles for women's dresses.

    The dress maker called the special dress a "4D dress". It is like the fabric(织物). It can turn into different kinds of shapes.

    The company, in Massachusetts, the USA, also made a smartphone and an app(应用软件). They can help women to control their dresses. If women use the phone and the app, they can change the colour, the style and many other things of the dresses. Isn't it very interesting?

    When she talked about her work, Jessica said, "There will be many more changeable dresses for women in the future. I am interested in making them too. I can't wait to make different kinds of new dresses for women."

    We always think that it's OK for us to leave our plants home during our vacation as plants won't scream like pets, right?

    A recent study done by a group of scientists at the Tel Aviv University has discovered that some plants will scream when they are under stress.

    The research was carried out on tomato plants and tobacco plants by cutting their stems (茎) and depriving (剥夺) them of water. A microphone was placed 10cm away from them. When their stems were cut, the plants started "screaming" between 20 and 100 kilohertz, and the scientists guess that this scream is probably meant to warn other plants nearby.

    When the tomato plants' stems were cut, 25 ultrasonic (超声的) pain sounds were recorded in an hour, and at the same time, 15 ultrasonic pain sounds were recorded from the tobacco plants. When they were deprived of water, the tomato plants recorded even more pain sounds with 35 pain sounds in an hour while the tobacco plants recorded about 11 pain sounds.

    The plants also acted differently to different kinds of stresses. For example, the tobacco plants gave out a stronger "scream" when they were deprived of water than when their stems were cut. But plants that were in no immediate (立刻的) danger gave out less than one ultrasonic sound per hour.

    The group of scientists said that plants are not as quiet as we had always thought, but in fact their voices are so high-pitched that we just can't hear them.

    Last year, another study has found out that plants feel pain when they are touched or hurt and they will give off a terrible smell.