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.

    Building an app is a big project. If you want to build the next great smartphone app, you need a plan. First, think about the kind of app that you want to build. Will your app be a game? Will it be for business? Then make a schedule(日程安排)for building the app. You need plenty of time for research before you are ready to build.

    Now you're ready to make the app. Building an app is like a puzzle(拼图)with many different parts. You can build it yourself or find a company to help you. There are many videos and websites that can teach you to build one. Some websites provide "building blocks" for app developers. As you build, you pick blocks from the website and put them in your app.

    After you build your app, you need to check it carefully. Look for bugs. Most apps have several problems to fix. Show your app to people. Ask their opinions. Mike sure everything works before letting people download it. There are so many tools that can help you build apps. Having the right tools will make the work easier. Now almost anyone can make a new app.

    Which of your two hands do you use 1 ? Very few of us can use 2 of our hands equally(相等地) well. Most of us are 3. Only about five people out of 4 hundred are left-handed. New-born babies can take things 5 either of their hands, 6 in about two years most of them use their right hands. Scientists(科学家) don't know 7 this happens. Scientists 8 that monkeys like to use one of their hands more than the other, but it can be either hand. Most of people use their right hands better and this makes life 9 for those left-handed persons. We live in a 10 world.

    China has recently published its first artificial intelligence(AI,人工智能) textbook for high school students in Shanghai to start AI lessons. Forty high schools around the country have become experimental bases for exploring AI education.

    The book, Fundamentals of Artificial Intelligence, includes the history of AI and how the technology can be used in areas such as facial recognition, public security and auto driving.

    Peng Yu is a teacher at the High School Affiliated(附属)to Shanghai Jiao Tong University. He took part in editing the textbook and said it would give guide to students. He said," The book has a good introduction to the area so that students can decide if they want to further study AI at college Students can also find out what they need to learn if they are interested in studying AI. For example, they have to learn Maths because it is the fundamental basis of AI."

    Peng said AI has improved the interest of many high school students already, but he still feels that they can learn much more by taking part in project—based learning programs. Peng is sure that everyone should learn some basic knowledge about AI because it will be part of our everyday lives. It is reported that China needs 5 million AI teachers to keep up with development in the future.

    Around the world, there are about 7,000 National Parks. Most of them cover huge areas of land where nobody lives. However, the National Parks in England include places where people live and work, as well as wild areas where there are few human activities.

    The National Parks in England are called "England's Breathing Spaces" because they are places where people can go to be in the open air, away from the dirt and noise of cities. They provide wonderful scenes of mountains, woods, grasslands and wetlands. And there are plenty of activities to do in all of the National Parks in England. Visitors can walk or ride bikes for fun. Many of the parks put on activities for families.

    Every year there are about 110 million visitors to the parks, bringing many benefits(益处) to the areas. At the same time, it creates problems, too.

    First, life can be difficult for local people. Car parks and roads are too crowded. Gift shops and cafes take the place of many everyday shops. Even house prices in some areas can become too high. Besides, country roads can be damaged, for too many people walk, cycle or ride horses on them. Roads can be rebuilt, but then they look less natural. Another big problem to the National Parks is litter. In the parks it is a danger to wild animals. Broken glass can also cause fires by focusing the rays of the sun. Such fires in wild places can be out of control.

    _______All National Parks in England are making more rules, which tell people how to take good care of their environment. If these rules are followed, the National Parks will be well kept and continue to give pleasure to many people for a very long time.

Practicing yoga(瑜伽) is a helpful, popular way to keep fit. It has many followers around the world. There are many kinds of yoga. You may have heard of "hot yoga" before. Now, in India, a new kind of yoga, water yoga, is becoming more and more popular among the local people.

In the city of Agra, people practice yoga in water. It is more difficult to practice yoga in water than on land. But practicing yoga in water can be good for your flexibility (灵活性).

Harish Chaturvedi, a lawyer, teaches people water yoga for free even the poor people can learn from him. "Water yoga can become more popular than other kind of yoga, because the body does not get tired so quickly," he said. "Everybody can learn to swim, but if they learn yoga at the same time, they will never feel tired."

"The level of Oxygen(氧气) is very high in water, and you will not have any breathing problem," he added.

Harish believes that water yoga really helps people to keep away from illness. He mainly trains children. He has classes at the swimming pool of a local sports room regularly. Many children are interested in it and come to team from him.

"Harish is very good at performing yoga in water," said Sudhir Narayan, a water yoga student. "He is teaching children free of cost and that is a very good thing."