10 . Billions of poor people around the world     1     (depend) on the use of wood for cooking. And as they take more and more firewood from wild areas, they are destroying habitats around the world. Wood collection is one reason why many animals have become endangered.

This is     2     Dr. Metcalf spends each summer in Africa. He wants to teach women and children in villages how to cook with the sun. He helped create Solar Cookers International. It’s an organization that introduces solar cookers to developing countries     3     teaches people how to use them.