修改时间：2022-01-20 浏览次数：57 类型：单元试卷
As everyone knows, animals are our friends. Of all the animals, we find that dogs are friendly to1.
Dogs are always staying2human beings. They are in different colours and3. There are many different kinds of dogs too. Hunting dogs can4people get more prey (猎物). The seeing-eye dogs can help 5people a lot. The police dogs can help the police.
Today it is6to imagine life without dogs. Maybe everyone is happy to see dogs. Dogs are good at7and smelling. Some dogs can find the people who are trapped (困) 8the broken houses. Some dogs can help take care of the houses of their owners (主人).9someone strange comes close to the house, they will bark to frighten (吓唬) him. Even some dogs can help look after small kids when their10are not at home.
In a word, dogs are our best friends among all animals.
There is good and bad news about the number of trees on our planet. The good news is that there are seven times more trees than we thought. A few years ago, scientists believed that the world had 400 billion trees. However, a new study from Yale University shows that there are around three trillion (万亿) trees. That's a three followed by 12 zeroes. That means there are about 420 trees for everyone in the world today.
The bad news is that thousands of years ago, the earth had six trillion trees. Humans cut down half the number of trees on the planet. Take Europe for example, it was a large forest thousands of years ago. Now much of it is cities and towns. And another 15 billion trees are lost each year.
Dr Thomas Crowther is one of the scientists from Yale University. He said the new number of trees from their study would change nothing. "The study only shows we need to do more to protect our forests," he said.
The earth is about 4,600 million years old. Human beings have lived on the earth for several million years, but during this period we have changed our planet a lot in many ways.
All over the world, people have cut down millions of trees, so more and more kinds of animals and plants are disappearing. In big cities, cars and buses have polluted the air. Factories have also polluted the land and the water.
It is important to the earth. But now air pollution is destroying it and that has made a very big hole in the ozone layer (臭氧层)
Carbon dioxide (CO2) in the air has increased a lot.It has formed a "blanket (毛毯)" around the earth.This makes our earth become warmer and warmer. Therefore, this causes the level of the ocean to rise.
All these problems are very serious. We must do something to stop our earth from being polluted.
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A. The heat from the Sun can't escape, so the temperature is rising. B. Too much harmful light from the Sun passes through it and reaches the earth directly. C. Some things we've done are very good for the earth while some are bad. D. Around the earth, there's a special kind of oxygen called “ozone”. E. It mainly comes from different kinds of burning materials. |
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