The air surrounding us is important to everyone. Without air, we could not exist. Everyone understands that. But air is necessary in many other ways — ways that are not always so obvious or widely known.
If we did not have air, there would be no sound. Sound travels through air. Where there is no air, there is no sound. Without air there would be no fire. There would be no automobiles, since motors need air in order to operate.
Without air, there would be no wind or clouds. The night time would be very cold and the days very hot. We would be forced to seek shelter from the sun, as there would be no atmosphere to protect us from the sun’s deadly rays.
In this huge ocean of air surrounding the earth, there is more energy than in all the coal, oil and gas we have on the earth. Electrical energy is collected in the atmosphere as water is collected and stored in a dam (大坝). The existence of electricity in the air has been known for centuries
A. air is important to human being
B. air is important to the earth
C. air is necessary in many other ways
D. air is necessary to the animals
The air surrounding us is important to everyone. Without air, we could not exist. Everyone understands that. But air is necessary in many other ways — ways that are not always so obvious or widely known.
If we did not have air, there would be no sound. Sound travels through air. Where there is no air, there is no sound. Without air there would be no fire. There would be no automobiles, since motors need air in order to operate.
Without air, there would be no wind or clouds. The night time would be very cold and the days very hot. We would be forced to seek shelter from the sun, as there would be no atmosphere to protect us from the sun’s deadly rays.
In this huge ocean of air surrounding the earth, there is more energy than in all the coal, oil and gas we have on the earth. Electrical energy is collected in the atmosphere as water is collected and stored in a dam (大坝). The existence of electricity in the air has been known for centuries
A. will become very cold
B. will do good to human beings
C. will become hot
D. will do harm to human beings
Healthy trees are important to us all. Trees provide shade, beauty, and homes for wildlife. Trees give us products like paper and wood. Trees can give us all these only if they are healthy. They must be well cared for to remain healthy.
Your trees’ trouble may be you yourself. People spend much time and money to plant and maintain trees. Trees improve the looks of homes, parks, business, and public buildings. Yet, people who love trees the most may be the ones who cause them injury. Of course, they do not do this on purpose. They are most likely not aware of the kinds of things that injure trees. There are many people-caused tree injuries. You should become aware of them and avoid them. Learn the things that can help to keep your trees healthy.
Healthy trees are beautiful. They make our world a pleasant place to live ill. Unhealthy trees are not as beautiful. They make our world less pleasant. Healthy trees help to cool and clean the air. They can even deade
A. beautiful
B. old
C. healthy
D. young
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