Title: Opcional

Text: Because of human activities, there is more carbon dioxide in the atmosphere today than in the past hundreds of thousands of years. Burning fossil fuels has released great quantities of carbon dioxide into the atmosphere. Cutting forests and clearing land has also increased carbon dioxide let into the atmosphere because these activities reduce the number of autotrophic organisms that use up carbon dioxide in photosynthesis. Cada párrafo será una prueba.

Save test: Use esta opción si usted desea compartir esta prueba (sólo para usuarios autenticados).