Lights out, phones on. Many teenagers reach for their smartphones or tablets at bedtime, but it may be a good idea to switch off before you hit the pillow.

    According to a study by researchers at Murdoch and Griffith Universities in Australia, using mobile devices late at night could harm teenagers' sleep and lead to an increased risk of mental health problems.

    The study was carried out on more than 1,000 Australian high school students aged between 13 and 16. It lasted four years as student participants moved from Year 8 to Year 11.

    During the study, students were asked what time of the night they received or sent text messages and phone calls, and how well they slept.

    The results are impressive. When the study started in Year 8, more than 85 percent of the students had a mobile pone and around one-third of these students never used phones after lights out. In contrast, 93 percent of Year 11 students had a mobile phone and only 22 percent of then had no late night mobile use when the study concluded four years later.

    As the levels of mobile phone use increased, there was a growth in poor sleep behavior among the students. Meanwhile, mental health problems also increased. Students in Year 8 who were more likely to use phones at night were found to have higher levels of depression (抑郁) and lower self-esteem (自尊心) one year later.

    Lynette Vernon, lead author of the study, explained that phones affect our sleep patterns because of the unnatural blue light they produce. This light could affect the level of hormones (荷尔蒙) in the body, disrupting (打乱) its balance.

     “The more you sit in bed and watch TV, play with your tablet, and play with your phone at three o'clock in the morning, the more these things affect the slow waves of your sleep pattern and give your poor quality sleep,” Mark Levi, a Sydney-based sleep doctor said.

    Based on the findings, the researchers suggested parents should focus on guiding their children's use of mobile devices.

    According to Vernon, the solution is not simply to ban teenagers from using their devices, but teach them better ways of using them

     “Back when they're aged 7 to 10, you have to be a role model. If you put your phone away at night and it doesn't go into your bedroom, it becomes normalizedin the household and you have a much easier job,” he told The Guardian.

    It is popular to travel by bike in China. China has a huge population. And it is said that there is at least one bike for every two people. Of course, many people in China ride bikes for sport or exercise, but it is also a much more commonly accepted means of everyday transportation, as compared to countries such as the United States.

    If you are living for a long time in China, chances are that you will want to buy your own bike so that you can use it whenever you want. Even if you don't use a bike for everyday transportation, owning one can be a great way to enjoy the sights in the countryside. However, if you are just visiting China, renting a bike can be a more convenient choice.

    It is important to choose the correct bike for your use. You will find that in China, the one-speed style of bike is popular. These bikes are great if you want to ride around in the city to see the sights. They are quite comfortable and easy to ride. You can often rent a bike for a day for about 15 dollars.

    However, if you wish to ride on some of the rural paths, a mountain bike style would be a better choice. They are great for different kinds of road surfaces, providing for a safer ride. If you are planning to have a wish to tour and still be able to carry packages with you, then a touring bike would be the best choice. These are the most expensive to rent, but are very suitable for carrying packages and even some of your luggage along with you.

    Sharon, Aged 22

    The most important thing to keep in mind when going into high school is to be yourself. Besides, I don't know what your middle school was like, but high school teachers will not care about things such as how much homework you already have in one night. It's best to just learn to deal with things and manage your time wisely so you can achieve everything you need to.

    Frank, Aged 21

    I think almost every kid feels both nervous and excited before their first day. You will probably love it. I know I did. You should join some sports or activities that will make your high school experience more enjoyable.

    Good luck!

    Eddie, Aged 20

    When I started high school I was really nervous too, especially since I had been homeschooled all through middle school and didn't really know anyone. I suppose the best advice would be to just relax. The first couple of days can be a little bit hard, but things will become easier before you know it.

    David,  Aged 19

    I am not going to lie. The first day is kind of frightening. But you'll get used to it. Don't be afraid of anyone; upperclassmen will pick on you more if you let them know you're afraid. Just take it easy. Making some friends and staying with them will greatly help you get used to high school quickly. After the first week it's really not bad at all. Don't worry.

    “I could see a huge flow (流动) of water, coming down fast from very high. I had no idea of shape, or situation, or anything. It was just so big.”

    These are the words of the great English writer Charles Dickens. He wrote them when he was visiting Niagara Falls. This waterfall is on the border (边界) of the United States and Canada. It is one of the largest in the world, and the largest in North America.

    Niagara Falls is on the Niagara River. The river divides just before the waterfall, and there are actually three waterfalls. On the American side are American Falls and Bridal Veil Falls. Horseshoe Falls is mostly on the Canadian side. The name comes from its shape — like a horseshoe, in a half circle. Horseshoe Falls is the widest of the three.

    People mainly know about Niagara Falls because of its size and natural beauty. However, the Niagara River is also an important source of electricity.

    In the 1890s, the Westinghouse Electric Company built a large power system (电力系统) on the river. Many other companies also hoped to use the land around Niagara Falls for factories and power systems. However, around the same time, many people began to work to protect the natural area. Soon, the governments of the United States and Canada got involved with it. They protected the land around Niagara Falls. They made parks — green, natural areas. No one could buy this land for factories. For hundreds of years, millions of people have visited Niagara Falls to enjoy its beauty.

    A man was going to open a shop selling hats. He wanted a good sign to put over his shop. He wrote:

    JOHN BROWN HATTER

    Makes and Sells Hats for Ready Money

    The first friend gave him the advice that the word "hatter" wasn't needed. So John crossed out the hatter. Then he came to another friend for advice. This friend said that it was not polite to say "for ready money". So he crossed out "for ready money'.

    The sign now said:

    JOHN BROWN

    Makes and Sells Hats

    One day a friend was passing his shop. He saw this sign and said that when a man bought a hat, he didn't ask who made it. So John crossed out "makes".

    But when another friend saw "John Brown sells hats", he said "Of course you sell hats. No one thinks you give them away."

    So, at last the sign read:

    JOHN BROWN

    Some people have a very poor sense of direction. Unluckily, I am one of them. I have visited a place many times but I may still get lost there the next time.

    When I was a little girl, I never dared to ask strangers the way. And so I used to walk around in circles and hope that by chance I would get to the place I was going to.

    Now, I am no longer too shy to ask people for directions, but I often receive helpless or even wrong information. So I try to avoid giving people wrong directions. If anyone ever asks me the way somewhere, I would say, "Sorry, I am a stranger here."

    Once on my way to work I was stopped by a man. He asked me if I could tell him the way to the Friendship Building. I gave him my usual reply. But just as I walked on only a few steps, I realized that he had asked the way to my office building. However, I had no time to turn back and look for him. I was rushing to meet with someone at my office and I didn't want to keep him waiting.

    When I just got to my office, the secretary(秘书) showed in the man who had asked me for directions. Imagine how embarrassed I was and how surprised he was when we saw each other at the first sight.