老师：Hello everyone. Great to see you all bright and happy. We mainly talk about what we should do at school to protect the environment. Last time that's not enough. There are many other actions that are bad for our environment. Let's look at the following pictures. Predict the main idea of the passage. Easily predict the main idea of the passage is about the environmental problems. From picture 1,3, and picture five. They are about too many cars, cut into many trees and porridge, too much waste water. Do you know the other two factors? Let's read the passage and the truth. The titles for paragraph.
老师：two to six 在我们略读为段落，选择小标题时要顺航快速移动眼睛，把注意力集中在关键词上，即与带血的小标题相关的词上。遇到生词尽量猜不出来的可以跳过去。如给出的这 5 个小标题，前三个因为我们前几课的积累，对我们来说可以轻而易举地确定下来后两个小标题里面的新单词。我们不要急着到字典中去查它们的意思，只要在阅读中找到与它们相对的关键词，就可以确定它们是哪段的标题了。
老师：give it a try。 By now.
学生：The earth is 4.6 billion years old. We humans have lived on the earth for only 35000 years. But during this period, we have changed our planet a lot. In many ways, some things we have done are very good for the earth, while others are bad. All over the world, people have cut down millions of trees. When it rains or when the wind blows, the earth is taken away. Forests have become deserts. So many kinds of animals and plants are disappearing. In big cities, cars and buses have polluted the air. Now many people in cities have health problems. Factories have also polluted the land and the water. As a result, many rivers and lakes are now dead.
学生：Around the earth, there's a special kind of oxygen called ozone 0,3. It is important to the earth, but now air pollution is destroying it and making a very big hole in the ozone layer. Too much harmful radiation from the sun passes through the hole and reaches the earth directly. This is very dangerous because this kind of radiation can cause cancer.
学生：Carbon dioxide, CO2 in the air has increased a lot. It mainly comes from burning oil, coal and wood. This has formed a blanket around the earth. The heat from the sun can't escape, so the temperature is rising. This is called the greenhouse effect. It causes the level of the oceans to rise and the climate of the earth to change. All these problems are very serious, so we must do something now.
老师：Did you all get that? Yes, you did quite well. For paragraph two can find its title, fewer trees, by the phrase, down millions of trees. For paragraph three, we can know its title, traffic pollution by cars and buses have polluted the air. For paragraph four, we can have its title, factory pollution by the sentence, factories have also polluted the land and the water. Paragraph five, we can get its title, the Oval Hole, by the sentence, but now air. pollution is destroying it。 And making a very big hole in the oval layer. Paragraph six, easily mak
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