Better think twice before choosing a password for email, online bank or shopping. Simple passwords are easy to be stolen.

    A password is like a key to your home. If someone steals it, he'll get chances to steal something else. We use passwords everywhere in our life. We are so used to passwords that we don't pay any attention to them until we lose or forget one.

    A study of 28，000 passwords recently stolen from a popular website showed that people often do the easy thing. It found that 16% took a first name as a password. Another 14% used the easiest keyboard combinations such as “12345678” or QWERTY. 5% of the stolen passwords were names of television shows or stars popular with young people. 3% of the passwords expressed feelings like “I don't care，” “Whatever，” “I love you，” or their opposite, “I hate you.”

    Robert Graham, who did the study, advises people to choose a password that is longer than eight characters with one capital letter and one symbol.

    Of course, safe passwords don't mean those hard to remember. Forgetting your password is sometimes a big headache for you. Maybe, the perfect password is easy for you and hard for others.

    Taking away a city's rubbish is a big job. Every day tracks come into a city to collect it. Most rubbish is made up of things we can't eat or use. If we kept these things we would soon have a mountain of rubbish.

    In some cities the rubbish is collected and taken outside of city to a dump. Often the city dump is placed where the ground is low or there is a big hole. The kitchen rubbish is broken into small pieces and sent into the sewage system. The sewage system takes away the used water from toilets, bathtubs and other places.

    To keep mice and flies away, some earth is used to cover the newly dumped rubbish. Later, grass may be planted on the rubbish-filled land. Finally, a house or a school may be built there, and then you'd never know that this had once been an old rubbish dump.

    In other cities the rubbish is burnt in special places. The fire burns everything but the metal. Sometimes the metal can be used again in factories where things are made of metal. The food parts of rubbish are put in special piles where they slowly change into something called humus, which looks like black earth. It is rich with the kinds of things that feed plants and help make them grow.

    March 20th is World Water Day every year. According to a report from the United Nations, more than half of the world's major rivers have serious water loss and are polluted.

    The Yellow River, the world's fifth longest river, watered some of the oldest farms on earth.

    {#blank#}1{#/blank#}Its source（源头）on Qinghai-Tibet Plateau is drying up. In most of the past 35 years, it didn't reach the sea.

    The Nile in Egypt, running 6, 650 km, is the longest river in the world.{#blank#}2{#/blank#}Now it is down to 2 billion m³ or so. Australia's Murray River reaches the sea only every other year. One fifth of America's Rio Grande has no water, either.

   {#blank#}3{#/blank#}

    Mostly it's damming（筑坝）and global warming that make rivers dry.{#blank#}4{#/blank#}Now about 45, 000 of them lie across the world's rivers. They hold back around 15% of the world's fresh water from running to the sea.

{#blank#}5{#/blank#}Warmer weather takes water away. The glacier（冰川）are becoming smaller. The source of the Yellow River is drying up because of it. Global warming has had certain effects on water sources. Droughts （干旱） happening around the world make people pay more attention to this fact.

    Artificial intelligence (AI, 人工智能) can help us make phone calls. It can guide us to where we want to go. It can play games. And now, AI can do even more things.

    Researchers from Microsoft have created the first machine translation system that can translate news articles from Chinese to English, Business Standard reported.

    According to Microsoft's official website, researchers tested the system by asking it to translate hundreds of sentences taken from news stories. Then, language experts compared the results to two translations that were done by humans. The experts concluded that the system's translations were as good as the human translations.

    Machine translation is always challenging. This is partly because different words can be used to express the same meaning. It can be hard to say which word is more “correct”.

    Experts used several methods to improve the system's translation abilities. “Much of our research is really inspired (得到启发) by how we humans do things,” lead researcher Liu Tieyan said.

    One method is called dual learning. In this method, the system translates every sentence from Chinese to English, as well as translates the sentences back from English into Chinese. This way, the system can improve itself and learn from its own mistakes. This is similar to what humans do to make sure their translations are accurate (准确的).

    Another method makes use of deliberation networks . The researchers taught the system to repeat the process of translating the same sentence over and over. Gradually, the system can improve the quality of its translations. This is similar to how people revise their own writing by going through it again and again.

    In earliest times, men considered lightning to be one of the great mysteries (神秘的事物) of nature. Some ancient peoples believed that lightning and thunder were the weapons (武器) of the gods.

    In reality, lightning is a flow of electricity formed high above the earth. A single flash of lightning 1.6 kilometres long has enough electricity to light one million light bulbs (灯泡).

    The American scientist and statesman, Benjamin Franklin, was the first to show the connection between electricity and lightning in 1752. In the same year he also built the first lightning rod (避雷针). This device (装置物) protects buildings from being damaged by lightning.

    Modern science has discovered that one stroke (闪击) of lightning has a voltage (电压) of more than 15 million volts (伏特). A flash of lightning between a cloud and the earth may be as long as 13 kilometers, and travel at a speed of 30 million meters per second.

    Scientists judge that there are about 2,000 million flashes of lightning per year. Lightning hits the Empire State Building in New York City 30 to 48 times a year. In the United States alone it kills an average (平均数) of one person every day.

    The safest place to be in case of an electrical storm is in a closed car. Outside, one should go to low ground and not get under trees. Also, one should stay out of water and away from metal fences. Inside a house, people should avoid open doorways and windows and not touch wires or metal things.

    With lightning, it is better to be safe than sorry?