Do you like drinking coke, coffee, juice or milk? Do you often drink them instead of water? However, of all the things we eat and drink, water is the most important. Not all of us understand this but it is quite true. Human body can go without food for a long time, but two or three days without water usually makes people die.

    Many people do not understand how much water the human body needs to work well. What is true is that many people do not drink enough, especially in hot weather. Most people drink only when they are thirsty but often need more water after they take exercise.

    Does anyone know what is the 65%-75% of human body? It is water. If we do not have enough water, we will feel tired and become ill. So, do you know what the best drink is? It's water.

    In most parts of the world, many students help their schools make less pollution. They join “environment clubs”. In an environment club, people work together to make our environment clean.

    Here are some things students often do.

    ◆No—garbage (垃圾) lunches. How much do you throw away after lunch? Environment clubs ask students to bring their lunches in bags that can be used (被使用) again.

    ◆No—car day. On a no-car day, nobody comes to school in a car—not the students and not the teachers! Cars give pollution to our air, so remember: Walk, jump, cycle or run.

    Use your legs! It's lots of fun!

    ◆Turn off the water! Did you know that some toilets can waste (浪费) twenty to forty tons of water an hour? In a year, that would fill a small fiver! In environment clubs, students mend those broken toilets.

    We love our environment. Let's work together to make it clean.  

    The government in China ended his one-child policy and let families have two children instead in 2015.

    A Chinese Communist Party statement gave a number of reasons for the change in policy. The statement said the change is meant to balance population development, stop a falling birth rate(出生率)and strengthen the country's labor force(劳动力). China, with the largest population in the world, started the one-child policy in 1980. But the government allowed only a small number of couples to have two children. For example, some families in the countryside could have two children, if the first-born is a girl.

    In 2013, the Chinese government gave other couples a chance to have two children if one of them was an only child.

Jiang Quanbao, a teacher and population expert, explained how Chinese families react(反应) to the newest policy. "Too many young people in the cities are no longer interested in having a second child," he said. "People in the countryside are more interested. But some of them are already allowed to have two children." At the end of 2014, China had a population of 1.37 billion people. A total of 800 million of them have jobs. But the labor market need of labor by the year 2050. With the two-child policy, an increase in births can solve this problem.

    Boys and girls, what do you think of the two-child policy? Do you want to have a new-born brother or sister?

    There is a popular belief that goldfish only have a three-second memory. But a 15-year-old schoolboy from Adelaide has just finished an experiment（实验）to tell us that it is not true. He shows everybody that the goldfish is smarter than we think.

    “I don't believe that they had a three-second memory because animals need their memory, so they build up over time a knowledge of where the food is,” said Roy Stokes, a student at the Australian Science and Mathematics School.

    He did the experiment in small tank（鱼缸）of goldfish. “I decided to get a bit of red Logo and just feed them next to that. Every day I'd put it in and spread food around it.” He said.

    “At first they were a bit scared of it, but by the end of the three weeks, they were actually almost coming before I put the food in.”

    After leaving the fish alone for a week, Rory placed the red Logo block in the tank again.

    “They remembered perfectly well,” he said.

    “They actually had a time faster than the average of the three feeds before I left.”

    The goldfish showed that not only could they store information, they also had the ability to get it back as a later date.

    Culum Brown, a research fellow at Sydney's Macquarie University, has studied fish behavior for more than ten years.

    He says his studies of Australian native fish show fish were intelligent creatures that know how to avoid enemies and catch food like any other animal.

    “The thing that I really liked about Rory's experiment is he not only got that classical conditioning going but the fact that he could get them next just to that specific coloured market. I thought it was really good.” He said.

E

    Artificial intelligence（人工智能）, or AI in short, is the science of giving computers and machines ability to think and work like humans. AI scientists and engineers have made a lot of cool technologies.

    AI is rapidly catching up with the human ability to read faces. As a result, facial recognition（识别）is used a lot in the world. Chinese police use this technology to identify criminals（罪犯）.Once they caught a criminal when he attended a concert. It also checks the ID of ride-hailing（网约车）drivers and lets people pay for things with a smile.

    AI is also used in self-driving cars, which are believed to be the future of driving. Most drivers may wave or nod at passers-by to let them cross the street, but self-driving cars don't have this ability. Carmakers are testing a light signal system to help them "speak" to humans. The system can show what self-driving cars will do. For example, if a driverless car is yielding（让路）, it will flash two white lights side to side. A rapidly flashing light tells passers-by that the car is about to speed up.

    Service Robots also show you know powerful AI is. Imagine this—you come back home from school and your robot housekeeper is waiting for you at the door. After dinner, he teaches you to play the piano, just like a real music teacher. Such thoughts will soon happen in the real world. In the future, more and more service robots will become good home helpers.

    AI is so powerful that it can help human beings and even replace us in many jobs.

    One of the hottest places on Earth is Death Valley. It's a desert valley in North America. The animals in Death Valley don't use technology to keep cool. They have special abilities that help them live there.

    During the day in Death Valley, it gets hotter than 100°F. The kangaroo rat rests all day in a hole in the ground. It covers the hole with grass to keep out the heat. The kangaroo rat comes out at night when it is cooler. This little rat is also very good at saving water. It gets all the water it needs from the food it eats. The Sun makes the desert sand very hot. One snake, called the sidewinder, can solve this problem. When it travels, the sidewinder bends (弯曲) its body into a "W" shape. Then it uses the bottom parts of the "W" like legs and walks sideways (向一侧). That way it touches only a little of the sand at a time, so the hot sand doesn't bum the snake. This strange way of moving is how the sidewinder got its name.

    A lot of water in the desert is too salty for most animals to drink. One kind of fish, the desert pupfish, can live in these salty water because it can drink the salt water.