It's very important that we all recycle. In nature, everything can be1again. For example, when an animal dies, it becomes 2animal's food. Nothing is wasted. But humans have created things like plastic bags 3can't be broken down by nature. Our rubbish kills animals and 4water and soil. 5we continue making too much rubbish, the problem will only get worse. If nature can't reuse the rubbish, we must recycle6.

    We should clean up the rubbish we've made because nature can't.

    Recycling is also the right thing to do for another reason. The earth is rich in natural materials like water and trees,7these materials are not endless. We use up our natural materials much8than the earth is able to reproduce them. For example, each year we cut9more that 6,000 square miles of forest. But it takes about 25 years 10a new tree to grow.

    Recycling can help us save the earth, so let's take action right now.

    The universe is really mystical(神秘的). Scientists have done lots of study about it but there is still much they haven't discovered.

    Scientists think that there 1 life on the earth for many many years. However, we haven't found life on any other planets 2

    There are eight planets going around the sun. The earth is one of them. There are humans, animals, plants and many other kinds of life on the earth. There is water and air, too. And compared to the other planets, the earth is not too 3 or too cold. None of seven other planets has av. environment like that of the earth.

    The sun and its planets are called the solar system, and our solar system is a small part of a 4 larger group of stars and planets, called the Galaxy or the Milky Way. There are 5 stars in the Galaxy, and our sun is only one of them.

    Scientists have also discovered many other galaxies in the universe. Their light has to travel for many years to reach us. So 6 is the universe? It is impossible to imagine.

    Scientists have sent spaceship to the planet Mars 7photos. They have even sent spaceships to travel outside 8 . However, no spaceship has traveled 9 to reach other stars in our Galaxy.

    When we see stars twinkling(闪耀) in the sky at night, we may think a lot:10 so many stars in the universe, is there life out there in space? If there is life on other planets, what life will be like there? What transports do they use to travel? Why don't they visit us? We do not know the answers…

    March 22nd is World Water Day. It started in 1993.It not only makes us think about the importance of water, but also calls on (号召) us to 1and protect water. Today, we're facing terrible water problems. Among them, wastewater problem is especially2.And the subject of World Water Day in 2017 is" wastewater".

    What is wastewater？It is used water. Usually, wastewater comes from homes,3, hospitals and so on. It is produced by different kinds of activities, including washing the machines, taking showers and using the kitchen. The rain also 4wastewater when it is running down the street during a storm. No matter where it comes from, this kind of water is sure to have 5harmful in it.

    6must we treat (处理)wastewater？Wastewater has a big influence on our life. It causes both illness for us and pollution for the environment. We must care for our environment and our own 7.

How can we treat wastewater？Different kinds of wastewater need different ways of treatment. Wastewater 8homes can be reused. Then there will be 9wastewater. Also, factory wastewater has to be cleaned 10it goes back to nature.

    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!

    Today more and more people live in cities. So there is usually little room in a city to grow food.1of the land in a city is used 2 homes, shops, roads and parks. Most food for city people is grown in the country. It is often brought to the city by3, train and plane. Some food 4 comes into the city by car.

    Water is5 thing that cities get from the country. Everyone needs water every day. We use a little of it for6, but we use even more to 7bathtubs(浴缸) and wash streets.

    The water used in cities comes mostly from the rain. But people8use the rain that falls on cities. The rain becomes dirty as it falls through dirty air. Once it hits city buildings or streets, the rain will pick up more dirt. It is not good for drinking or bathing.

So cities must reach out to the 9 country for water. There the rain falls through air onto trees and grass. The fallen rain runs 10 rivers and lakes. So it is important to keep both cities and the country clean.