20.空氣汙染 Ⅱ
段落大意：自然汙染物和人類廢棄物都會汙染空氣。
Air pollution occurs when wastes dirty the air. Natural pollutants （汙染物） include dust, soil particles and naturally occurring gases. Most of the wastes that cause air pollution are created by human beings. These wastes are mainly in the form of gases or particles of solid or liquid substance, which result chiefly from burning fuel to power motor vehicles. Industrial processes and the burning of garbage also contribute to air pollution.
21.空氣汙染 Ⅲ
段落大意：人口激增、工業的高速發展及機動車、飛機等都對空氣造成了汙染。
The rapid growth of population and industry and the increased use of automobiles and airplanes have made air pollution a serious problem. The air we breathe in has become so filled with pollutants that it can cause health problems. Polluted air also harms plants, animals, building materials and fabrics （織物）. In addition, it causes damage by altering the earth’s atmosphere.
22.空氣汙染 Ⅳ
段落大意：工廠等排放的各種物質均會造成空氣汙染。
Our environment is affected by our daily actions. The earth is plagued（受折磨） with land, air and water pollution. Some of the problems we face are deforestation, nuclear waste, acid rain, global warming, overpopulation and animal endangerment. Air pollution has many different causes. Power stations, oil refineries （精煉廠）, chemical plants, and steel mills（製造廠） contribute to about 140.million tons of pollutants into the air every year. Automobiles account for at least 80.percent of air pollution, making it the heaviest polluter. Another type of air pollution is acid rain. Acid rain is formed when sulfur （硫） and nitrogen （氮） are released from factories, automobiles and power plants. The sulfur and nitrogen rise up into the clouds and come down as rain that is contaminated （汙染的）. It damages forests, crops and soil and kills fish and animals that live in water.
23.人類活動對生物多樣性的影響
段落大意：人類的生存離不開生物多樣性，但目前因為人類的種種活動，各種動植物正在急速滅絕。
Human life cannot exist in the absence of millions of species in biological systems. However, as humans, we live in a period of the greatest loss of plant and animal species since the mega-extinctions （巨型滅絕） of the Jurassic （侏羅紀的） Period 65.million years ago. Harvard University biologist E.O. Wilson estimates that “50,000.plant and animal species disappear each year due to tropical deforestation, expanding agriculture, and human settlement.”Human activities impact the environment, including clearing forests for agriculture, air, land and water pollution, and the introduction of invasive or non-native wildlife species. If land and wildlife are largely influenced by human activities, humans risk fragmenting （打破） habitats and pushing wildlife to extinction.
24.保護環境的行為
段落大意：個人的良好行為，包括不亂扔垃圾、實行垃圾回收等，可以教育他人，並引導他人也來保護環境。
Through your lifestyle and manners, you can make others aware of the environment and its constant fragile （脆弱的） state. Many people don’t understand that their actions are actually doing harm. By not littering, others will see how easy it is to actually walk to the garbage can. When you pick up trash, your peers will notice how much nicer and cleaner your surroundings seem, and will in turn want that for themselves. When you recycle, they’ll see how simple and easy it is, and what a difference it makes. They will see that there are alternative ways to make their homes and personal environments a lot healthier to live in. Eventually they will see that there is a need to preserve the environment for ourselves and our future, and reap （收獲） the benefits by doing so. Eventually they’ll understand that they hold the future in their hands, and that in the end it’s their choice.
25.熱帶雨林的重要作用
段落大意：熱帶雨林是人類的寶貴財富，對動植物的生存具有重要作用，而且能為人類帶來巨大的利益。
“In every sense, a standing rainforest supplies more economic wealth than if it were cleared. Yet deforestation continues at an alarming rate.”（Tropical Rainforest Coalition, 1996）. Rainforests have played a significant role in shaping modern biology. The destruction of the rainforests will influence the fate of all species including various kinds of plants and animals. Many people do not understand the long-term consequences of losing the earth’s rainforests. Rainforests have provided human beings with many natural resources and medicines. Traditionally, there are three major causes of the destruction of rainforests:logging, farming and ranching （牧場經營）.
26.土地資源的減少
段落大意：人類活動造成土地資源減少，我們應該采取措施保護土地資源，以維持人類的生存和發展。
Though most of the world’s surface is covered by water, since the earth is so large, there doesn’t appear to be a shortage of land. However, when one begins to think of land in terms of human resources, that is, a producer of food, a provider of wood and other raw materials, one realizes that many parts of the earth are either too lacking in nutrients （營養物）, too high in elevation （海拔）, too prone （易於…的） to flooding, or too cold for humans to live. Furthermore, habitable lands are becoming less abundant due to desertification （沙漠化） （the expansion of deserts due to the misuse of land）, and rising sea levels. Since humans aren’t the only species that need land, it isn’t surprising that this resource is becoming limited for other forms of life too. In part as a result of this stress on living things, we have witnessed extinctions of animals at a rate of thousands of species per year. Since these losses are largely due to human actions, such as deforestation and non-native species introduction, many are beginning to pay attention to how we use and protect land. Recent ecological research has also rung alarm bells for the future well-being of life on this planet.
27.二手煙對人類健康的威脅
段落大意：二手煙會導致多種疾病，包括心髒病等，甚至會造成人的死亡。
Exposure to secondhand smoke is called involuntary smoking, or passive smoking. Passive smoking causes at least 3,000.known deaths a year according to the Environmental Protection Agency. Passive smoking has been consistently linked to an increased risk for coronary （冠狀動脈的） heart disease and may be responsible for more than 30.cardiovascular （心髒血管的） deaths annually in the US alone.