Robots seem very new to most people. But they have a 1 history. A Greek scientist made the first robot. You may 2 robots in some movies. The robots in the movies are usually stronger, faster and 3 than people. In real life, most robots are used in factories. They can do lots of dangerous, difficult or4 jobs. Some people can't look 5 themselves and robots can help them. For example, some people can't see, and they use a guide dog to help themselves move. But now scientists are making a 6 to help them.

    Robots are also used in American hospitals. At one hospital, a robot 7 meals from the kitchen to the sick people's rooms. It never loses its 8 because it has a map of the hospital in its computer system(系统). 9 the future, robots will even work in space. But robots will 10 take the place of(代替)people but only work for people. They can, however, help us in a lot of different ways.

    I think that the world will be an easy place to live in. We1have machines and robots and they will2us do all the3jobs, and we don't have to do things4washing dishes and5the beds, though we won't have any dishes at all. Maybe we will just throw the dishes away after each meal. I6that doctors will be able to7us alive8a long time. I hope that when I am 80 years old, there9something that can keep me alive for1080 years, so I will live to be 160 years old.

    Many of us enjoy watching animals in the world. But do you know they can teach us?

    Geese(大雁), for example, teach a very good lesson about1  In the fall, Canada geese fly to the warm south to 2 Canada's cold winter. They lift off in no order. Yet3 they form a V shape, with one bird leading the group.

    This V shape allows geese to 4 energy(能量). When the front bird moves its wings up and down, the resulting force of the air lifts the next one. This continues down the line. The bird 5has the hardest job. When it gets 6 , it moves behind, and another bird moves into the lead. By sharing the role, the group can travel great distances (距离). Geese flying in a V shape can fly 70 percent farther without 7 than birds flying alone. During the long flying travel, geese communicate with one another. They honk(鸣叫)to 8 the birds up front to keep up the speed I (速度). They also ,cheer each other up 9working toward a common goal (目标).

    What have we learned from the lovely geese's experience and skills?10 together! Whether it is our personal lives or our jobs, we need other people. We need the spirit of teamwork!

    When the weather is hot, you go to a lake or an ocean. When you are near a lake or an Ocean, you feel cool. Why? The sun makes the earth hot, but it cannot make the water very hot. Although the air over the earth becomes hot, the air over the water is still cool. The hot air over the earth goes up. Then the cool air over the water moves in and takes the place of the hot air.

    Then you may ask, "Why is the ocean full of salt?" Scientists will say that the salt comes from the rocks. When the rocks get very hot or very cold, they crack (爆裂). Rain falls into the cracks. The rain then carries the salt into the earth and into the rivers. The rivers carry the salt into the ocean. And then you may doubt, "But the ocean does not get more salty every year. Scientists are not sure about the answer to this question.

    We know a lot about our world. But there are still many answers that we do not have, and we are curious about them.

    What's a spacewalk? Any time an astronaut gets out of a spacecraft(航天器) while in space, it is called a spacewalk. Astronauts go on spacewalks for many reasons. For example, experiments can be placed on the outside of a spacecraft. This lets scientists learn how being in space affects(影响) different things. By going on spacewalks, astronauts can also fix things instead of bringing them back to the earth to fix.

    When astronauts go on spacewalks, they wear spacesuits to keep themselves safe. Inside spacesuits, astronauts have the oxygen(氧气) they need to breathe and the water they need to drink. To keep the astronauts and the spacecraft safe, the astronauts must leave and go back to the spacecraft through a special door. When on a spacewalk, astronauts use safety tethers to stay close to their spacecraft. Tethers are like ropes, connect the spacewalkers with the spacecraft. They keep astronauts from floating(漂 浮) away into space. Another way astronauts stay safe during spacewalks is by wearing a SAFER. SAFER is worn like a backpack. It helps an astronaut move around in space.

    How do astronauts train for spacewalks? One way is by going for a swim. Floating in space is a lot like floating in water. Astronauts practice spacewalks underwater in a huge special swimming pool. For every one hour they will spend on a spacewalk, astronauts need to train seven hours in the pool. Another way astronauts practice for a spacewalk is by using virtual reality(虚拟现实). It looks and feels just like a spacewalk.

    Today, only three countries have finished spacewalks independently. They are Russia, the United States and China. The first person to go on a spacewalk in the world was Alexei Leonov from Russia. Zhai Zhigang is the first Chinese astronaut to go on a spacewalk. The world record of spacewalks is held by Russian astronaut Anatoly Solovyev. He has been on 16 spacewalks and spent more than 82 hours outside in space.

Nature is amazing! Take a close look at the world of insects, and you'll discover many unbelievable things. Consider butterflies (蝴蝶), for example. They have beautiful wings and magical flying skills. On summer days, you always see them flying freely over flower gardens and wild fields.

But did you know how butterflies become the flying insects? It is one of the wonders of nature. In the beginning, the mother lays a small and colourful egg on a leaf or stem of a plant. It is hard to believe that the egg will become something completely different in a few days. It becomes a walking insect. This insect is called a caterpillar. It now has legs, eyes and a large body. A new life begins. The caterpillar can eat, walk and see. But it is still not a butterfly.

Soon, after growing big, the caterpillar makes a cover for itself. It covers itself in the nice protective blanket (保护层) and goes to sleep. This is known as the "pupa (蛹)" stage. After some time, the blanket breaks and a wet butterfly appears. It now has six legs, a mouth, eyes and wings. Shortly, the beautiful butterfly spreads (张开) its wings and flies away. After a few weeks, this butterfly lays her eggs, and the cycle (循环) begins all over again.

This is just one example of the wonders of nature. Look around the natural world, and you will learn many truly amazing things.