The Milu deer is a kind of animal with large horns(角). They were very common in China long ago. They lived together and ate grass and the soft parts of trees. In the past, people did not protect the Milu deer and killed them for food or sport, so they disappeared(消失) from China .

      Luckily before all of them disappeared, the Duke of Bedford(贝德福特公爵) took some to Britain. The Milu deer like the cool, wet weather in England and their numbers increased(增长) year by year. As a result, when in1985, the government of China wanted to bring back the Milu deer, the Duck of Bedford was able to help. The first deer came back to China to the Nanhaizi Milu park near Beijing and to Dafeng, Jiangsu Province.

      Since they returned to China, their number has grown quickly .There are now so many of them that a new park has been opened for them in Hubei Province. Now the Milu deer live in the wildlife parks and have good protection. We hope that one day they can live in the wild again.

    Animals can move from place to place, but plants cannot. When an animal is under attack, it can run away or fight back. Plants certainly cannot run away, and they have no teeth or claws. But plants can protect themselves in both physical and chemical ways.

    Some plants have their own ways to keep animals away. For example, the leaves of the holly(冬青) have sharp prickles(刺) that discourage grass-eating animals. Holly leaves on lower places have more prickles than leaves on upper places. This is because the lower leaves are easier for most animals to reach. Some plants, such as the oak trees(橡树), have thick and hard leaves that are difficult for animals to eat. Some grasses may contain a sandy material, and eating such grasses wears down the animals' teeth. Many plants also have chemical defenses. Some plants produce chemicals that taste bitter(苦) or cause an unpleasant reaction. Some plants may fight against an attack by increasing the production of these chemicals. When a worm bites a tobacco leaf (烟叶), the leaf produces a chemical smell. Many plants depend on both physical and chemical defenses. A certain plant in China, for instance, has prickly leaves, and each prickle has poisonous water(毒液). Only one experience with this kind of plant will teach an animal to stay away from it in the future.

    Do you know the way of using wind power to make electricity? There are many advantages({优点) of using wind to make electricity. Here're some of them.

    First, it may be one of the cheapest ways to make electricity. Second, it can make and store hydrogen gas. The most important one is that it won't pollute the environment. Besides, the wind power can be reusable.

    But large wind farms might kill birds too, because birds always fly into the wind turbine(风力涡轮机). Scientists are looking for ways to stop it.

    Experts said that by the middle of the 21st century, wind power could supply more than 10% of the world's electricity. Wind really helps us a lot.

    American researchers have successfully developed a way to clean waste water without chemicals. The technique uses green plants. The tests were carried out at waste treatment centre. The scientists put plants in narrow containers inside a glass building. One end of each container was a little higher than the other end. Waste water was directed down the containers through the plants' thick roots as we expected. The roots absorbed the waste in the water and used it for food. At the same time the plants produced natural gas. The gas could be collected and sold as fuel(燃料).

    Four places in Florida are already using green plants to clean their waste water.

    Have you ever had trouble sleeping in a new place? Lots of people do. And now researchers from Brown University in Rhode Island think they know why. They found that one-half of the brain "remains more awake" than the other half when people are trying to sleep in a new place.

    The sleep findings were reported in Current Biology by Brown University. In their report, the researchers said many people report that they have a harder time sleeping the first night at a hotel or other places outside their home. They call it "first-night influence". "In Japan they say, 'If you change your bed, you can't sleep,'" said Yuka Sasaki, one of the report's writers. "You don't sleep very well in a new place. We all know about it."

    The researchers measured brain waves (测量脑波) for 35 volunteers over two nights in a laboratory. The two nights were a week apart(间隔).They found during the first night the left half of the brain was more active than the right half. This was during the first deep-sleep period, the researchers said.

    Sasaki said a lot of questions remain.

    Researchers did not keep measuring brain waves all night long. So, they don't know if the left half keeps "watch" all night, or whether it" works in shifts (轮换) with the right half later in the night" .They also do not know why the brain activity, at least during the first period of deep sleep, is always on the left half.

    For some, this research may be calming. It is good to know that our brain is "looking out for us" in a new place. But it may not help with sleep. That brain activity, at least according to this new research, makes it harder to get the sleep people need to wake up well rested in the morning.