TOEFL Listening: ETS-TOEFL听力机经 - Y4K31J6449433Z7EP$

Why does the professor mention planting trees in specific locations? A. To introduce the most historically effective conservation strategy. B. To provide an example of farming practices that use excessive water. C. To begin a list of underused but more productive methods of farming. D. To give an example of effective farming tactics in arid regions.