There are many wetlands in China and some of them have become the world's important wetlands. The Chinese Yellow Sea Wetlands are among them. They are in Yancheng, Jiangsu Province. They are home for many different kinds of animals. The world's largest Milu Deer Nature Reserve is in them. More than 700 Milu deer live freely there. There are not many red-crowned cranes in the world, but every winter you can see some in the Red-crowned Crane Nature Reserve in the Yellow Sea Wetlands.

The temperature in the wetlands is usually neither too high nor too low. There is a lot of rain and sunshine, too. They are really good places for wildlife. Offering(提供) food and home for some special kinds of animals is not the only reason why we need to protect wetlands. Wetlands are important because they also prevent flood. But some people want to change the wetlands to make more space for farms and less space for wildlife.

    Luckily, more and more people are beginning to realize the importance of wetlands and wildlife. Every year, on February 2nd, many activities are held to tell people more about wetlands.

    Most people agree that trees look nice, but not everyone knows that trees can also help cities save money. A few years ago, the US Forest Service studied trees in Chicago. They found that just one tree can save a city hundreds of dollars over its lifetime.

    Trees can save money by helping people save energy(能源). Trees stop the sun shining on buildings. They also block(挡住) the winter wind. That helps people use less energy to make their homes or offices warm or cool. Saving energy is saving money.

    Trees have another way to help a city save money. When it rains, there will be a lot of water in a city's sewers (下水道). Cities need lots of money to clean that water. But before the rainwater gets to the dirty sewers, trees can take some into themselves. With the help of trees, there is less water to clean.

    Alsten Chase has written a book about Yellowstone National Park. He is worried about the damage the fires can do to the park. He is also concerned(关心) about the park rules. These rules say that nature should decide what happens to the park. Alsten also writes that the elk herd(马鹿群) has grown too big. The elks walk on the riverbanks. They eat the new grass and roots of baby trees. The beavers(河狸) need the trees to build dams(坝).

    The dams raise the water levels. Higher water levels put more water into the soil. Wet soil helps plants grow faster. The plants offer homes and food to other animals.

    Chase thinks that the park rules would work only in a park with natural settings. He believes that Yellowstone has had an artificial(人为的) setting for a long time. The native people left. The wolves were taken away and other animals were removed. The areas of land were fenced off(隔开) and other animals added. He thinks the park rules that let herds grow too big and the fires are hurting the nature of the park.

    The park manager thinks the rules are good and that the park will be fine. Chase thinks the way the people run the park should be changed.

    You know how much your telephone has changed over the past 10 years? Your car will change even more than that in the next 10 years. One of the biggest changes is that cars will drive themselves.

    "We certainly have the technology for it now." says Andrew Poliak of automotive(机动车辆的)technology supplier QNX." We expect self-driving cars to be a mainstream thing between 2020 and 2025."

    The American company Google has been working on self-driving cars for years. These cars are already on the roads in the United States and are truly self-driving. They have to steering wheels(方向盘）or pedals(踏板). Last week, the police ordered one of Google's cars to stop for driving too slowly on a public road. The car was not breaking any law, so no one was punished.

    Another American company, Tesla, added an "Autopilot" feature to its cars last month. With the Autopilot turned on, the vehicle drives itself. The car will speed up, slow down, brake and drive by itself. You can take over driving any time by turning the steering wheel or touching a pedal. The car uses sensors to know when driveway changing is safe and whether it should speed up or slow down.

    Tesla Autopilot is made for cross-country driving. It keeps you in the driveway and helps you avoid hitting other cars. It does not work well on local roads, for it will not stop at a red light or stop sign.

    Reporter Carolyn Nicander Mohr tried the Autopilot feature of a Tesla earlier this month. She had a hard time trusting the car to do what it should do. She thought about disabling the Autopilot feature many times during her trip. She wanted to take control at every bend in the road and hit the brake when the car in front of her slowed down. Yet the car drove perfectly.

    Other companies are working on self-driving cars, too. Marcedes-Benz, Audi, BMW. Volvo and Toyota all have plans for such vehicles.

    Many people know Shanghai's beautiful night view(景色), especially the colorful lights from the buildings. Light helps us see and makes the environment more beautiful. However, too much light becomes a kind of pollution but many of us pay little attention to this pollution or even ignore it. In fact, it causes a lot of problems. Light pollution can be almost as bad as carbon dioxide pollution.

    Too much light can do harm to our health. First, it can make us feel bad and we can't sleep well. Second, lights need electricity, and creating electricity will give off greenhouse gases. This affects the air and causes breathing problems. Third, study shows people living under bright light for long can have cancer more easily.

    Too much light may be even harmful to wild animals. Thousands of birds die from it each year. Some hit into the light buildings, because they can't see clearly in the strong light. Some birds sometimes lose their ways in the bright light Sea turtles(海龟) can't find the dark beaches to lay their eggs.

    To protect humans and wildlife, we should take measures to reduce the use of lights at night.

    A black hole is a place in outer space with very strong gravity. Gravity is a great force(力量) that shapes the universe. On Earth, gravity makes apples fall from trees. It keeps your feet planted on the ground. The gravity in a black hole is much stronger. It is so strong that nothing around it can get away from it, not even light.

    Black holes are invisible. We can't actually see them because they don't throw back light. But scientists can find them with space telescopes(望远镜)and special tools. The strong gravity makes nearby stars move in a certain way. By studying how the stars move, scientists can find out if they are flying around a black hole. Strange things happen around black holes. This makes black holes a popular subject of science fiction(科幻)stories, although they are very real.

    A black hole forms when a star dies. The star falls in on itself and turns into a very small point. Because of its small size and huge mass(质量), the gravity will be so strong that it will pull light in and become a black hole. Black holes can grow huge as they continue to pull other things in and "eat" them. Many scientists believe that there are super-massive black holes at the center of galaxies, including the Milky Way.

    The idea of the black hole was first suggested by two different scientists in the 18th century: John Michelle and Pierre-Simon Laplace. In 1967, a physicist named John Archibald Wheeler came up with the name “black hole". Studying black holes can tell us many things about our galaxy and help scientists answer questions about the universe.