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.

    Air is a colorless, tasteless and invisible（看不见的）gas that is around us. An "empty" drinking glass and an "empty" room, in fact, are not really empty. Each is filled with air. When the glass is filled with water, the water pushes the air out of the glass.

    Air, as a gas, has no definite shape, but because it is matter, it takes up space and it has weight. It is easy to prove that air is something that takes up space. Stuff a piece of dry cloth（布）into the bottom of a glass so that it will not fall out when the glass is turned upside down. Push the upside down glass, holding straight up and down, into a jar of water till the glass is completely covered. When the glass is taken out of the water, the cloth is still dry. The air inside the glass shows that it takes up space and keeps the water from coming in.

    The kangaroo is the world's largest living marsupial (有袋动物). It was first found on the island of southwestern Australia. The animal was given its name by a famous English tourist in the 18th century.

    The kangaroo may be 7 feet(2.1m) tall when standing upright and the male can weigh as heavy as 200 pounds(90kg). The female (雌性) is smaller and lighter than the male. The kangaroo's head is small, but its ears are large, and its fore feet are really small. The animal has strong back legs and long tail.

    The kangaroo usually covers from 5 to 10 feet(1.5 to 3m) with each jump. The female is usually faster than the male. The mother kangaroo has a pouch (育儿袋) in its abdomen (腹部). The baby kangaroo grows up in the mother's pouch slowly.

    The kangaroo lives on grass and other plants. It is always moving from one place to another, lying down to sleep on the ground during the night. It likes to enjoy the warm sunshine. When it's in danger, it can use its back legs and strong tail to protect itself.

    Answer the following questions with No more than 6 words.

    Smog(雾霾) is a big problem in many Chinese cities. But it seems that besides wearing a mask, few of us know what has caused the smog and what to do to beat it. Chai Jing, a former news hostess with China Central Television, discussed the questions in her documentary Under the Dome.

    The 103 - minute film was published on major Chinese video - sharing websites on Feb 28. In the film, Chai visits polluted places and talks to officials and scientists. She comes to the conclusion that burning too much coal and oil are the main causes of PM2.5 and smog.

    To make things worse, according to Chai, the coal and oil we are burning is of poor quality and don't meet the standards for environmental protection. Therefore they have produced more harmful gas to pollute the air.

    To solve the problem, Chai suggests that we should clean our coal and oil or replace them with cleaner energy such as natural gas. In her film, Chai also pointed out that ordinary people can do something to help control smog too. For example, we live a greener life by using more public traffic. Or if we see things that could harm the environment, we can try to stop it. In one scene from the film, Chai sees a dirt mound in a building site exposed in the air, and asks the person in charge to cover it. When she sees a restaurant cooking without any suitable filter facilities, she calls the hotline 12369. The restaurant installed the filter a week later.

    Chen Jining, the new minister of environmental protection, praised Chai. "This film encourages ordinary people to care about the environment. This is what we need in the future. "

    Fraser Island is in Queensland, Australia, about 200 kilometers north of Brisbane. It is about 120 kilometers long and 240 kilometers wide. It is a very important island because it is completely made of sand. In fact, it is the largest sand island in the world. There is no airport on the island, but there is a long beach along the east coast. Planes arrive and leave from here.

    The sand makes unusual shapes. There are hills made of sand called sand blows. Nothing grows on them. They move one or two meters a year from the northwest towards the southeast of the island, getting bigger and bigger. At other places on the island, such as Rainbow Gorge, The Cathedrals and Red Canyon, the sandy rocks have different colors. Sometimes the rocks are so brown that they turn the sea brown, like coffee.

    Surprisingly, the sandy island has a lot of different plants and animals. There are dark forests—eucalyptus woods, beautiful flowers and over a hundred lakes. There are many kinds of birds, like owls and curlews. There are many animals there, too, such as crocodiles, flying foxes and wild dogs called dingoes.

    About 500,000 people visit the island every year to see the island's beauty and nature. People enjoy camping and hiking（徒步）there. Unluckily, the visitors create problems. They damage plants and frighten animals. Their sun cream（防晒霜）makes the water dirty. So it is necessary to manage the visitors. For example, people may not use motor boats or go fishing in the lakes, and they need official papers to drive there.