1. .......... forms of energy are environmentally-friendly methods of producing usable sources of energy. For example, people are trying to harness wind and solar sources of energy.

2. When a lot of pollution enters the atmosphere, we sometimes experience .......... rain. This is when harmful chemicals are released along with water vapor and rainfall.

3. .......... occurs when a large variety and number of plants and animals coexist in a certain area. We have to protect this so that ecosystems are not disrupted.

4. Trash that is comprised of organic and natural substances and that can be broken down into harmless waste is called .......... . Once broken down, the harmless material can then be absorbed back into the environment without any bad effects.

5. Nowadays, many people are exploring and using alternative .......... sources (other than gasoline sources) in transportation sectors including natural gas, electricity, ethanol and methanol blends.

6. Many people are worried about .......... change. This is when changes in temperature and weather patterns occur in a particular area. Scientists think there is a connection between fossil fuel emission levels and this phenomenon.

7. Some governments around the world have implemented emission .......... . This is a decided upon limit placed on levels of toxic and harmful emissions that one company or country, in general, is legally permitted to release into the atmosphere.

8. Dump sites or .......... are waste disposal areas. We should try to reduce our consumption levels so that we don't have to create more of these areas in the future.

9. The .......... effect refers to air pollutants, such as carbon, nitrides and methane gases, that trap much of the world's heat under layers of these pollutants. As a result, this phenomenon has caused a steady increase in the earth's atmospheric temperature.

10. People have used .......... fuels such as oil, coal and natural gas for a long time. These limited resources were created when ancient life forms decomposed. However, we have to find other forms of energy in order to save the planet.