Grade 9 Unit 2 Topic 2 Section C

The earth is 4.6 billion years old. We humans have lived on the earth for only 35 000 years, but during this period, we have changed our planet a lot in many ways ^[1]in many ways: 在许多方面；用许多方法. Some things we have done ^[2]we have done: 此处是定语从句，省略了关系词that/which，修饰things are very good for the earth while others are bad.

All over the world, people have cut down ^[3]cut down: 砍倒；削减；减价；夺去…活动力 millions of ^[4]millions of: 数百万的；成百万的 trees. When it rains or when the wind blows, the earth is taken away ^[5]take away: 带走，拿走，取走. 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 ^[6]health problems: 健康问题.

Factories have also polluted the land and the water. As a result ^[7]as a result: 结果, many rivers and lakes are now dead.

Around the earth, there’s a special kind of oxygen ^[8]oxygen:US: [ˈɑksɪdʒən]   UK: [ˈɒksɪdʒ(ə)n]  n. 氧；氧气 called “ozone”(O3). It is important to the earth. But now air pollution is destroying it and making a very big hole ^[9]hole:US: [hoʊl]  UK: [həʊl]  n. 孔；洞；坑；漏洞 in the ozone layer ^[10]ozone layer: n. 臭氧层. Too much harmful radiation ^[11]radiation: US: [ˌreɪdiˈeɪʃ(ə)n]   UK: [.reɪdi’eɪʃ(ə)n]    n. 辐射；放射线；辐射的热（或能量等）；放射疗法 from the sun passes through the hole and reaches the earth directly ^[12]directly: US: [daɪˈrektli] UK: [daɪ’rek(t)li]   adv. 正；立即；立刻；直接地. This is very dangerous because this kind of radiation can cause cancer.

Carbon dioxide ^[13]Carbon dioxide: n. 二氧化碳 (CO2) in the air has increased a lot. It mainly comes from burning oil, coal and wood. This has formed ^[14]form: US: [fɔrm]  UK: [fɔː(r)m]  n. 形式；表格；形状；样子   v. 组成；建立；组织；产生 a blanket ^[15]blanket: US: [ˈblæŋkɪt]  UK: [‘blæŋkɪt]  n. 毯子；毛毯；厚层；厚的覆盖层 around the earth. The heat from the sun can’t escape ^[16]escape: US: [ɪˈskeɪp]   UK: [ɪ’skeɪp]   n. 逃脱；逃避；逃跑；溢出  v. 逃避；逃走；避开；泄漏 so the temperature is rising ^[17]rise: US: [raɪz]  UK: [raɪz]   v. 上升；增长；提高；升起    不及物动词  . This is called “the greenhouse effect ^[18]the greenhouse effect:  n. 温室效应 ”. It causes the level of the oceans to rise and the climate of the earth to change. ^[19]cause sb. to do sth. : 导致某人做某事

All these problems are very serious, so we must do something now.