4. Air Pollution

　　Air pollution is one of the major problems of the modern world. A great deal of energy is needed to run the factories of modern industrial nations. Automobile, trains, planes and busses need energy, too. Nearly all of this energy is produced by burning fuels. The burning produces wastes, some of which remain in the air, causing air pollution.

　　Scientists are finding ways to stop air pollution especially in big industrial areas and densely-populated cities. They are studying new ways of generating electricity that may be less damaging to the environment. In the meantime, many power plants are being modernized to give off less polluted material. Also, engineers try to design and locate new power plants to do minimum damage to the environment.

　　However, it may be that we still have a long way to go before we have a "clean" world. Nearly all of the countries are trying hard to prevent and control air pollution. There indeed seems to be no end to tasks that environmentalists will be required to do. People will continually find new ways to control pollution.

    更多信息请访问：新浪四六级频道 四六级论坛 四六级博客圈

　　特别说明：由于各方面情况的不断调整与变化，新浪网所提供的所有考试信息仅供参考，敬请考生以权威部门公布的正式信息为准。