“Dreams may be more important than sleep. We all need to dream” some scientists say. Dreams take up about one quarter of our sleeping time. People have several dreams each night.

    Dreams are like short films. They are usually in color. Some dreams are like old films. They come up over and over again. That may be the dreamer worrying about something. Dreaming may be a way of trying to find an answer.

    Some people get new ideas about their work from dreams. They may have been thinking about their work all day. These thoughts can carry over into dreams.

    Too much dreaming can be harmful. The more we sleep, the longer we dream. The mind is still at work when we dream. That is why we may have a long sleep and still tired after waking up.

    Many animals hide to stay alive. They hide in many ways. Some animals hide in leaves; some animals hide in snow. Usually their colors or shapes help protect them. It's hard to see an Arctic bear in snow. Its white fur helps protect it. Chameleons(变色龙) can hide by changing colors. Their skin turns the same color as what is around them. Some chameleons can change colors in five minutes.

    Many animals try to look bigger than they are to stay alive. Some animals can make other animals think they are very big. If they look very big, animals that are looking for food will run away. Bears can walk on two legs. They look very, very scary. Some animals will run away from them.

    Many animals try to stay around other animals. This helps them stay alive. Zebras stay close together so that they can help each other look out of danger. Seeing many stripes at once can also confuse animals that want to eat them. Some birds stay in a circle, each toward a different direction. In this way they can also help each other stay alive by looking around for animals that many want to eat one of them.

    Sophia is a robot in Saudi Arabia. She made history at a meeting that was held in the country on Oct 25. On that day, she became the first robot in the world to get citizenship (公民身份), according to The New York Times.

    In the future, Sophia may have the same rights as a human Saudi Arabian citizen.

    Sophia looks like a human woman. In 2015, a US company built her and gave her an artificial intelligence system (人工智能系统). This means Sophia can talk and act like a human. She also has the ability to learn from people, books and the Internet.

    "I will do my best to make the world a better place," Sophia said at the meeting.

    But not everyone is happy with Sophia's citizenship. Some think robots like her could be dangerous. They could become enemies of humans if they go out of control.

    For this, Sophia said she also had values like wisdom and kindness. "Don't worry, if you're nice to me, I'll be nice to you," she said.

    Autumn in Tibet is very beautiful because there are many fresh and bright colours everywhere.

    In north Tibet, one can travel several hundred kilometres by car and cannot see even a person. No one can be found in the north of Shuanghu-only treeless fields and grasslands. Warm autumn days bring life to all of nature. Wild animals become active, and Tibetan antelopes like to play near the lakes. When they run, sometimes they can reach 80 km an hour, leaving the hungry wolves far behind.

    Autumn in south Tibet is very different from that in north Tibet. Mount Qomolangma in southwest Tibet, the highest mountain on Earth, is world-famous for its beauty. It is over 8, 000metres high. There are over 2,300 kinds of plants and about 300 different kinds of wild animals on Mount Qomolangma.

    Many scientists think that the Earth is getting warmer and warmer. If the change continues, the natural world and human society will face danger. Scientists believe human activity is responsible for the climate change. We produce too many greenhouse gases. They keep heat in the air and make the Earth warm.

    Many of the world's governments agree. And they want to solve the problem. So from 7 to 18 December, 2009，they held a conference in Copenhagen, Denmark to talk about global warming and climate change.

    Representatives(代表) from 192 countries and regions went to the meeting. Although they have not reached an agreement, the Copenhagen Accord(《哥本哈根协议》) was an important beginning to save the Earth. It was made by a small group of countries including China，the USA，India, Brazil and South Africa. Some other countries at the conference also showed support.

    What are the key points of the Copenhagen Accord? The accord limits global temperature increases to 2C by 2050. Scientists think it could help the world to avoid serious climate change.

    The accord also says that developed countries must promise to cut greenhouse gas emissions(排放) to the UN by 31 January, 2010. The accord asks developed countries to give money to help developing countries.

    Many countries and organizations are disappointed that the conference didn't reach a legal document(法律文书). And they think the accord is not clear enough about its goals.

African leaders are worried that the goal of a 2℃ global temperature increase isn't good enough, because it will mean a much higher increase in temperature across Africa. This could cause big problems like food and water shortages across the continent.

    Still, UN Secretary General believes the conference was an "improvement".

    "Finally we reached a deal," Ban said," the accord may not be everything everyone had hoped for, but this is an important beginning."