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.

    What will the world of the future be like? There are plenty of people who are happy to give their opinion of what we will be doing in 2050. Here are two predictions about the world of tomorrow.

    When we dream about the future, many like to think of owning a personal flying car. The advantages are obvious. This technology would allow total freedom of movement. We could fly at 480 km per hour, avoiding traffic lights and busy roads. However, some people believe there will be problems with traffic control. If the cars become popular, there is likely to be air traffic jam. Another big problem is mechanical failure. What will happen if the cars stop working? These are problems we must expect if flying cars become a reality.

    Three-dimensional printing is another new technology with exciting possibilities. 3D printers are used to build an object with liquid plastic.

    They build the object layer by layer until it is complete. Car companies already use 3D printers to make life-size models of car parts, and medical companies use the technology to make man-made body parts. As we move into the future, 3D printing will revolutionize the way we shop, the way we manufacture and the way we treat sick people. The disadvantage is that such equipment will be extremely expensive.

    So in the future, we might be able to fly to work or print out new shoes. Although there are some problems to solve before this will be possible, we can certainly dream of a world where technology makes life easier and safer for millions of people.

The name of every British town and city has a long history. 

Two thousand years ago, most people living in Britain were Celts（凯尔特人）. Even the word "Britain" is Celtic. Then the Romans arrived and built camps. These camps became cities called "castra". This is why there are so many place names in England that end in "-chester" or "-caster". Manchester is one example. 

After the Romans left Britain, it was attacked by Anglo-Saxon people and became its new owners. These people were from the area that is now Germany and the Netherlands （荷兰）. The names of their villages often ended in "-ham" or "-ton". Some got their names from the leaders of the villages, so Birmingham, for example, means "Beormund's village". 

Twelve hundred years ago, Vikings（维京人） came to England. They traded with the Anglo-Saxons but lived in their own villages. These often ended in "-by" or "-thorpe". The name "Kirkby" means "a village with a church（教堂）" and Scunthorpe was the village of a man called Skuma. Finally, in 1066, England became Norman（诺曼人的）—the Normans gave us the place name "grange", which means "farm". 

And how about London? Experts cannot agree! The Romans called the city Londinium, but they were not the first people there. People once believed that the United Kingdom's capital city was named for the castle（城堡） of a king called Lud, but this is almost impossible. Our best guess today is that the name comes from a Celtic word meaning "a fast-flowing river". 

Recently, researchers have found that dolphins know their own names much like people. Dolphins talk to one another with whistles (口哨) and calls. Scientists have known that the animals also use unusual whistles to name each other. They had thought that dolphins only heard each other's voices. However, the scientists didn't know that dolphins listen for their names too.

To test this idea, the researchers caught 14 dolphins and recorded their name calls. The scientists then copied each dolphin's voice. When the changed recordings were played, the dolphins replied strongly to the names of their relatives and group members. They paid no attention to the names of dolphins they did not know.

Dolphins live in large groups that grow and change. Each dolphin's unusual whistle helps it quickly find a friend or a family member, or call for help. Understanding their calls requires learning. It's a skill that's seen in very few animals, which include humans and elephants.

Elephants, for example, communicate with sound. Their sounds can be heard by other elephants miles away. Dolphins, too, communicate with each other by making sounds like this. Elephants also communicate by moving their head, feet and trunk (象鼻). In much the same way, dolphins communicate by their movements. They often touch each other to express friendship.

Unlike dolphins, elephants also communicate by their great sense of smell. They can recognize other elephants by the smells they have.

Why do dolphins and elephants share the gift of communication? Scientists think it may be because they are social and smart animals. Both have strong family relationship. Now, whether they also have nicknames(绰号) is another question!

If you go to the forest with friends, always stay with them. 1 you don't, you may get lost. If you really get lost, this is what you 2 do: sit down and stay where you are. Don't try to 3 your friends—let them find you by staying in one place. 

There is 4 way to help your friends or other nearby people to find you. Give them a signal（信号）by shouting or whistling,（吹口哨）three times. Stop. Then shout or whistle 5 times again. Any signal given three times is a call for 6 .

Keep up the shouting or whistling 7 three times together. When people 8 you, they will know that you are not just making noise for 9 . They will let you know that they have heard your signal. They will give two shouts, two whistles or two gun shots（枪声）. When someone gives a signal, it is 10 to a call for help. 

We know exercise is important（重要的）in our life. Everyone needs to exercise. Doctors say doing sports is beneficial for us. Sports can make our body strong. Children should also do some sports. It's good for them. If children often do sports, they can be stronger and taller. Doing sports is easy. Here is some advice（建议）for you.

You can walk, run or only jump. These are easy ways. Every day you walk to the classrooms and have PE class.

Don't do sports too much at a time. Try all kinds of sports and look for one, two or even three sports you like. People exercise for an hour every day have better sleep and more energy（能量）.

You can also exercise at a gym or on the sports field. In the gym, you can play basketball, play tennis or play badminton. After school, you can run or play football on the sports field. Exercise can be fun. It can make you happy.

Friends can exercise together. You can do sports with your friends at any place you like. You can also join the running club together.

As you can see, you can try different ways to do exercise. And Just do it!