The passage: Humans need oxygen to breathe, and trees are vital sources of oxygen. Humans also need trees for various purposes such as wood for fuel and making furniture. As a result, trees have to be cut on a massive scale. This process is known as deforestation. In order to keep the balance between the constant demand and supply of trees, humans need to plant more trees through different processes such as afforestation or reforestation. The process of promoting forest growth is known as "forestation." When trees are planted in barren lands it is called afforestation. And, when trees are replanted in places where forests have been affected by deforestation, it is known as reforestation. Nowadays, reforestation is not only utilized in deforested areas, but it is also utilized as an alternative for natural forest habitats. In countries like Finland, companies manufacturing wood products or paper are required to plant an equal or higher number of trees to make up for those they cut down. To do this, they employ summer workers who plant trees in large numbers. Over the years, many governmental and nongovernmental groups have launched programs to promote forestation in several countries. How does the author develop the central idea in paragraph 3? A. The author describes how deforestation can affect a whole country. B. The author presents the difference between afforestation and reforestation. C. The author explains the procedure to stop deforestation in natural forest habitats. D. The author gives an example of how reforestation can be implemented successfully.