Across
- 5. /the increased levels of atmospheric carbon dioxide produced by the use of fossil fuels
- 6. / can be used again after they have been treated using a special industrial process
- 7. / able to be maintained at a certain rate or level
Down
- 1. / not depleted when used
- 2. being decomposed by bacteria or other living organisms
- 3. / the color between blue and yellow in the spectrum
- 4. / not harmful to the environment